It appears that TOR was developed, funded, and has been supported by the US government. Interesting article below.
I know people who say they use it for privacy- whether business or (in the case of one whack-job) "so the government can't track my posts on second ament forums.).
But let's face it- most TOR traffic is probably related to illegal stuff.
I'm willing to bet that TOR browsing isn't quite as anonymous as people might think.
http://pando.com/2014/07/16/tor-spooks/