New Scientist has discovered that Pentagon's National Security Agency, which specialises in eavesdropping and code-breaking, is funding research into the mass harvesting of the information that people post about themselves on social networks. And it could harness advances in internet technology – specifically the forthcoming "semantic web" championed by the web standards organisation W3C – to combine data from social networking websites with details such as banking, retail and property records, allowing the NSA to build extensive, all-embracing personal profiles of individuals.
Full article here. It goes on to discuss the prospect (still some time off in the distance) of the agency mining all on-line data about almost everyone, a project that might be feasible once semantic tags are added to most web information.
Meanwhile, if you're wondering how secure your data might be in the hands of the government, consider the recent theft of 26.5 million veterans and active-duty military personnel's names, social security numbers, and dates of birth (and more) from the home of a Veterans Affairs official. Looking up the links just now, I see that in the past week alone there have also been reports of data thefts involving the Department of Energy, the IRS, and possibly Medicare. NSA is more secure than these, one expects, but when the government gathers your data, you never know where it's going to wind up.