When Google Public DNS launched in late 2009, it was only ever supposed to be an experiment. But yesterday, Google announced that it's now the most popular public DNS in the world, handling over 70 billion requests per day.

To use Google engineer Jeremy K. Chen's own simile, as expressed in the official blog entry, DNS - short for Domain Name System - is like the Internet's phone book. When you put a URL into the browser, the DNS service looks it up and matches it to an IP address. Google Public DNS aims to be the most complete, fastest, and most secure listing of its kind out there for users all over the world.

In fact, Chen writes that 70 percent of Google Public DNS traffic comes from outside the US, thanks to existing nodes in North and South America, bolstered support in Europe, and all-new nodes for regions like Japan, Australia, India and Nigeria.

Of course, Google critics are wondering what good could come of the search giant having access to even more user data - in this case, a log of every single website that Google Public DNS visitors go to, all day, every day.

Now, Google says that it "never blocks, filters, or redirects users, unlike some open resolvers and ISPs," but, well, here's InformationWeek's rock-solid summary of its privacy policy:

Google also maintains a separate privacy policy for Google Public DNS. The company says it maintains two sets of server logs related to the service: temporary and permanent. The temporary logs contain user IP addresses and those are deleted in 24 to 48 hours (barring a court order to the contrary). The permanent logs, which contain city-level location data but nothing personally identifiable, are retained for at least two weeks. A small random sample taken from the permanent logs is kept indefinitely.

It's still unclear if Google Public DNS' privacy policy will be streamlined into Google's streamlined, unified document that's going live on March 1st, but regardless, it seems extremely likely that Google will stick to its guns as far as not sharing that data with anyone else. And on a slight tangent, I highly doubt that we'll see Google Public DNS added to that unified privacy policy, given the comparatively unique legal precautions it's already caused Google to take.

In the final analysis, the measure of how okay you should be with Google Public DNS and its privacy implications depends on whether or not you feel like Google is, in fact, evil. In the meanwhile, Google's holding the line that it protects user privacy at all costs.