Robert Epstein is Senior Research Psychologist at the American Institute for Behavioral Research and Technology (http://AIBRT.org) and the former editor-in-chief of Psychology Today magazine. A Ph.D. of Harvard University, Dr. Epstein has published 15 books and more than 200 articles on artificial intelligence and other topics. The views expressed here are entirely his own.

An editor at a major news magazine (not U.S. News) told me recently that Google can monitor people only when they sign in to a Google platform – Gmail or Google+, for example. Not so, I replied. Google can and does monitor people – perhaps upwards of 90 percent of Internet users worldwide – whether they use a Google product or not, and most people have no idea they're being monitored.

To make my point, I pursued a hunch. I expanded the header of the last email the editor had sent me. The header you normally see contains just four fields: From, To, Date, and Subject. But most email systems allow you to see much more. When you expand a header, you see many lines of technical information, including the names of the various computer servers through which the email passed on its way to you.

Sure enough, the editor's email had been routed through a Google server. How and why this routing was put in place, I don't know, but it appears that all outgoing emails from the magazine's staff run through Google, a company that has been known to scan email content. If you've ever received targeted ads that seem related to recent emails you've sent, you were probably scanned. The company can hardly deny that it scans; Buzz, the failed social network Google launched in 2010, was built entirely around information in Gmail messages that revealed who was friends with whom.

Just how extensive are Google's tracking activities? When I started cataloging them, I was amazed. Here is a partial list of tracking methods Google is known to use. I'd wager that the list of tracking methods we don't know about is much longer.

The search engine. Every search you conduct using Google's ubiquitous search engine – for medical or mental health information, an update on your favorite mayoral candidate, the schedule of your church's potluck dinner, how to handle kids' tantrums, the cure for halitosis or the latest sex toys – allows the company to track your interests and, over time, build a detailed dossier that describes virtually every aspect of your character, food preferences, religious beliefs, medical problems, sexual inclinations, parenting challenges, political leanings and so on. In other words, when you use Google's search engine, Google's gotcha.

Even if the company doesn't know your name, it can still track your searches by reading codes, such as your IP address, that are unique to your computer or current location. Through cross-referencing, the company can eventually find your name, address, and telephone number, too. When you use the search engine or most any other Google product, Google also installs an identifier cookie on your computer that makes you easier to track. And get this: Google reads and stores every letter you type into its search bar as you are typing (think: m-a-r-i-j-u-a), so even if your good judgment suddenly kicks in and you don't hit "enter," the company still records what it thinks you were looking for.

Google uses your search history to send you personalized ads. That's how it survives, after all. About 97 percent of the company's revenues are from advertising. Google justifies this business model, which could be viewed as fundamentally deceptive, by insisting that it's providing a unique and valuable service: sending vendors your way who precisely fit your current needs and interests.

Email. When you use Gmail, Google's email service, the company scans the content of your emails and the email addresses of your correspondents. Google's Gmail system also scans your incoming emails, even the ones coming from Yahoo and Hotmail. If you feel safe because you've deleted emails you regretted sending, think again. Google never erases its own copies, even copies of the drafts you decided not to send – even copies of incomplete messages you didn't save as drafts. And then there are those Google servers, which route the emails of thousands of companies that apparently don't mind running the risk that their emails will be scanned. So whether you use Gmail itself, write to someone who uses Gmail, or, in many cases, simply email, Google's gotcha.

Google+. If you use Google+, you are voluntarily telling Google a great deal about your personal life, including, at times, current and intimate details. Yes, the same is true with Facebook, but when it comes to dossiers, Facebook is a toddler at play compared with Google.

Chrome. This is Google's browser, introduced in 2008 to compete with Internet Explorer, Safari, Firefoxand other browsers. Why did Google bother to introduce yet another free browser into a somewhat crowded market? Because with Chrome, Google can track every website you visit directly – that is, without first passing through its search engine. The search engine on its own left a significant gap in the company's knowledge about you; it only revealed areas in which you needed more information. Chrome allows Google to track your activities in areas of your life that are so well established that you don't need to research them – the regular contact you have with your bank or employer, for example. Google might never have been able to track those kinds of activities without the help of Chrome.

Even in so-called "incognito" mode, Google has programmed ways to track you. If, for example, you use Chrome to put a link to one of your favorite websites on your desktop, when you click directly on that link, the window that opens is not in incognito mode. Gotcha.

Firefox. What? How can Google track you when you're using a competing browser maintained by a non-profit organization? It can do so because before Firefox takes you to your destination, it first checks to see whether that website is on Google's blacklist, an ever-changing list of about 600,000 websites that Google's bots have identified – sometimes mistakenly – as dangerous. No government agency or industry association ever gave Google the authority to maintain such a list, but it exists, and Firefox uses it. Thus, Google is alerted when you visit websites through Firefox. Even more disturbing is the fact that Mozilla, the organization that maintains Firefox, receives 85 percent of its $163 million in annual income from… that's right, Google. In return, Firefox makes Google its default search engine.

Safari. In 2012, Google was fined $22.5 million by the Federal Trade Commission for illegally tracking users of Apple's iPhone, iPad and Macintosh computers by essentially hacking Apple's Safari browser. The big fine solved the problem, right? Not at all, because Safari, like Firefox and other browsers, uses Google's blacklist to check the safety of websites.

Android. And why did Google develop its own mobile operating system, in this instance competing primarily with operating systems developed by Research in Motion (for Palm devices) and Apple (for the iPhone)? Because operating systems are even more deeply embedded into computing devices than browsers. Everything you type, touch, and swipe runs through the operating system, which gives Google full access to your digital activities. When you're online, Android can upload whatever Google tells it to, and when you're offline (which, these days, is hardly ever for mobile devices), Android can store whatever Google tells it to store for later uploading.

YouTube. Google, Inc. bought YouTube in 2006 for $1.65 billion, almost certainly because YouTube unveiled yet another set of insights into consumer preferences. When you spend hours on YouTube skipping from right-wing manifestos to horror movie trailers to Lady Ga Ga videos, Google's gotcha.

Google Analytics. More than half the world's most popular websites use Google Analytics to collect data about who is visiting their pages. Visitors have no idea that Google Analytics is even present, but Google is tracking every one of them. To put this another way, if you visit, well, most any website – that's right, Google's gotcha.

Google AdSense. In an attempt to monetize their web pages, millions of website owners now sprinkle small ads provided by Google throughout their legitimate content. The ads are, in theory (but often not in practice), related to whatever news story, food recipe or celebrity bio you're reading, making it somewhat likely that you will eventually click on one of them. Okay, I know what you're thinking: When you click on one of those ads, Google's gotcha, right? Not so. Google's gotcha the moment you load a page containing an AdSense ad. When you click on an ad, the company just gets more detailed info.

Google AdWords. As if those little ads weren't enough, Google also now allows website owners to embed targeted Google ads into words scattered throughout their textual content. When you load a page that contains any of those words, Google's gotcha, and when you click on any of those words, Google's got more.

Widgets. They're everywhere and multiplying like tribbles: tiny icons that allow you to notify your friends on Facebook or your colleagues on LinkedIn that the web page you're on is worth visiting. When you click on the G+ widget… that's right.

Google Street View. Google vehicles have now traveled millions of miles in 48 countries to take pictures of homes and businesses – visual information that's easy to cross-reference with the dossiers of home and business owners.

For a long time, though, the real treasure trove for Google was not in the photos but in the information its Street View teams were skimming from unencrypted Wi-Fi networks: passwords, emails, browsing histories, financial information and more. After the Federal Communications Commission discovered in 2010 that Google had been collecting information this way for at least three years in more than 30 countries, it secured a promise from company officials to discontinue the practice and fined Google $25,000 (yes, that's all) for impeding its investigation. More recently, the attorneys general of 38 states settled a lawsuit against Google for its Street View snooping for $7 million.

Google Maps. They're embedded on about a million websites. And when Google is present on a web page, it can track people who visit that page.

Google Glass. Due out in time for Christmas 2013, this is a mobile computer mounted on the frames of eyeglasses which will follow your verbal commands and help you make sense of what you see by, say, displaying reviews of a restaurant that's within your field of vision. In other words, Glass will give Google access to what you say, what others around you are saying, and what you see.

As for the future, think science fiction. The company's recent ingestion of the startup company Behavio will soon give it the power to track your location 24 hours a day, as well as to predict where you will be and who will meet you there – hours, days, or even weeks into the future. And then there are those little DNA projects: Google's recent takeover of key search and storage operations for the Sequence Read Archive, a massive public repository of DNA data, as well as its funding of at least two Silicon Valley companies that provide DNA mapping services for consumers. When DNA profiles become part of people's dossiers, Google will have crossed a potentially frightening threshold: it will know far more about people than they know themselves – what diseases people are likely to get (think of the marketing opportunities), what their racial origins are, which dads have been cuckolded. The possibilities are endlessly outrageous.

If you think I'm overstating Google's intrusions or misrepresenting Google's motives, think again about the revenue model. Virtually all of Google's income is from targeted advertising. Every major company expenditure, therefore (think YouTube), almost certainly has to feed the beast. In the consulting work I've done from time to time, I've more than once had the breathtaking experience of sitting in on high-level planning sessions. Revenue concerns come first. Top executives don't sit around saying, "Golly, what's the next cool product we can develop." Instead, in Google-land, the conversation is probably more like: "We now know A, B, and C about people. How can we find out about D?" A question like that would prompt answers such as: "Simple – let's buy YouTube" or "No problem – let's develop a browser" or "Let's call in the product people and see what they've got that can help us."

Is all this tracking legal? Here is what a Google executive might say: "We are protected by our Terms of Service agreement, which in turn incorporates our Privacy Policy – legally binding contracts that are easy to access on our website. We realize that almost no one has ever read these documents, but, hey, no one ever reads their mortgage documents or credit card contracts either, and they're certainly valid. Our agreement states that when you use any of our products or services – even if you're not aware you are using them – you agree to let us track you. It's that simple."

In other words – silly you – you gave Google permission to track you simply by engaging in activities that allowed it to track you.

The terms of service agreement also says that the information you give the company "and those we work with" (who's that, exactly?) can be used for almost any purpose. And the privacy policy states that Google can share your dossier with just about any individual or agency based on the company's "good faith belief" that doing so is required by law or, incredibly, that doing so will "protect…the rights, property or safety of Google."

In other words, piss us off and we can release a dossier about you as thick as a phone book (figuratively speaking). Could such a contract be valid – one that is all at once so invisible to users and so maddeningly all-encompassing or even threatening? This is for judges and regulators to decide in coming years.

In the mean time, I guess Google's ... well, you know.

Read the U.S. News Debate: Should Probable Cause Be Required for Police to Use Cell Phone Location Data?

Read Anson Kaye: Constitutional Hypocrisy on Gun Control and the 4th Amendment