Here's a news flash: Google employees love bacon, Mountain Dew, and Doritos, while Microsoft employees are partial to Capri Sun, butter, and Orville Redenbacher popcorn (separately and in combination, one assumes).

How do we know this? Thank data mining firm Rapleaf, which -- for reasons that surpass understanding -- decided to peer into the shopping carts of Google and Microsoft employees and offer up the insights hidden within.

[ Also on InfoWorld.com: Is Rapleaf getting a fair shake or a bad rap? Don't answer until you read Cringely's earlier report "Online advertisers are selling you out." | For a humorous take on the tech industry's shenanigans, subscribe to Robert X. Cringely's Notes from the Underground newsletter and follow Cringely on Twitter. ]

Per the Rapleaf blog:

We looked in our database for data about people with an @google.com or an @microsoft.com email address, and we created a sample of approximately 6,000 Google employees and 16,000 Microsoft employees. After anonymizing the data, we worked with data from a loyalty cards aggregator to evaluate the employees' purchase trends at grocery stores. For each company, we looked at the percentage of customers who purchased major grocery store products and compared the percentages side-by-side.

Other fascinating tidbits: Microsofties buy more vitamins, while Googlers load up on the fresh fruits and veggies. Employees in Redmond are more likely to be older and married, with kids. As a result, they're also more likely to have higher household incomes.

The RapLeaf report [PDF] goes on to analyze the reasons for all this (employees who enjoy gourmet meals in the Googleteria are more likely to splurge on snacks; married people with kids tend to buy more Capri Sun) and talks up the wonders of how data mining can personalize your shopping experience -- by, say, spitting out discounts for Doritos if your email address ends in @google.com.

The bigger takeaway, in my humble opinion: If you thought your supermarket loyalty card was only knocking 30 cents off that overpriced carton of yogurt, think again. It's also a window into your soul.

How can your supermarket habits hurt you? Imagine your insurance company perusing your shopping records. Then you get a letter in the mail: Gee Jim, I see you've been packing on the Ben & Jerry's Chubby Hubby lately. Cool it on the lard, fatboy, or we'll double your insurance premiums.

Or the divorce attorney for your soon-to-be-ex wife clocking how much beer you buy in order to persuade a judge you're a bad influence on the kids.

This isn't just theoretical. In the most infamous case, a Washington state firefighter was arrested for arson in 2004 because his Safeway Club Card was used to purchase the same brand of firestarter used to set the blaze. (He was later released.)

Of course, we're not just talking about shopping records. Companies like Rapleaf specialize in combining this shopping data with publicly available information (such as voter registration and property records) and tidbits culled from your Web surfing history, Facebook, and more.

Rapleaf offers the usual assurances about keeping this data private and anonymous. Then again, it was outed last fall by the Wall Street Journal for collecting a host of highly personal and personally identifiable information about some of the people in its database, including their political and religious beliefs and their attitudes toward tobacco, gambling, and adult entertainment (not to mention pork products). Rapleaf was also one of a few dozen companies "inadvertently" passing Facebook and MySpace IDs to ad networks, in violation of those services' privacy policies.

You'll have to forgive me then if I don't exactly take comfort in Rapleaf's assurances. The only thing keeping data miners like Rapleaf from handing over your entire personal dossier is that nobody has slapped them with a court order or written a big enough check yet. It's bound to happen eventually.

Don't want to be followed around the Piggly Wiggly by companies like Rapleaf? Use a loyalty card filled with false information and pay cash when possible. You also might want to lay off the bacon and buy more fruit -- just in case.

Do data miners worry you? Post your thoughts below or email me: cringe@infoworld.com.

This article, "The difference between Microsoft and Google -- it's not what you think," was originally published at InfoWorld.com. Track the crazy twists and turns of the tech industry with Robert X. Cringely's Notes from the Field blog, and subscribe to Cringely's Notes from the Underground newsletter. For the latest business technology news, follow InfoWorld.com on Twitter.