StunnedMonkey
Plinker
Simply put, you are not anonymous on the Internet. Especially not to any government entity (Law Enforcement or otherwise).
Exactly. The "government" could, if they desired to spend the time and money, track down virtually anything someone has posted, done, or visited on the Internet. Whether any particular individual or case is worth that level of effort, well who knows. But there's nothing that would remain anonymous if they wanted it badly enough. Nothing.