Templeton emphasizes that he doesn't know exactly how any of the search engine systems are designed, but -- given typical designs -- there are many different ways that someone with the right access and knowledge could make a retroactive correlation between search terms and personally identifiable information. Considering that search terms can reveal personal information that ranges from medical prescriptions to religious beliefs and political preferences, that's not an association many of us would be happy to see.

Even if you didn't provide any personal information, an IP address alone could be traced back through a reverse DNS lookup to the Internet service provider and city of the IP address, according to Danny Sullivan, editor in chief of Search Engine Land, a blog dedicated to search news. Contacting the ISP could result in a positive identification of the account holder by finding out which account accessed the search engine at the time recorded in the search log.

Last year, reporters at The New York Times didn't even need an IP address to track down the identity of an AOL user when AOL published anonymous search logs of 500,000 users over a three-month period. The identification was made possible simply based on the specificity of the search terms the user queried, such as real estate searches in the small town where she lived. (If you have any question as to what collected search terms reveal about an individual -- accurate or not -- check out those AOL search logs.)

Hello, George Orwell?
If all this sounds Big Brother-ish to you, you're not alone. Individual users, consumer interest groups, government regulatory committees around the world, and privacy groups are growing increasingly worried about how much personal data search engine firms retain and what they could do -- or be forced to do -- with this information. In recent months, Google seemingly hasn't been able to make a move without drawing speculation and suspicion about its ability to construct personal portraits of user behavior.

Several consumer interest groups have filed a complaint with the Federal Trade Commission regarding Google's acquisition of DoubleClick. The groups claim it would give Google unprecedented insight into consumer behavior because it could track both people's Internet searches and their Web site visits. And when Google released its History feature, which associates individuals' search and page visitation histories with their account information, some observers, such as veteran blogger Anil Dash, called it both "brilliant" and "scary."

"With the release of Web History, especially in the context of its recent acquisitions and announcements, Google may have crossed the line where regular users start to react with skepticism and caution instead of unabashed enthusiasm," Dash says in his blog (see "Google hostile to privacy, group says").