Very few people are actually capable of being anonymous on the net. What they have some little control over is the amount of effort necessary to learn their identity. Someone who really wants to know who they are, and has some resources, can find out.

One spammer found out the hard way: he thought that using a freemail service that didn't include the sender's IP address in the header would protect him. He'd have done better to pick one where I didn't know the head of Security.

(OK to unscreen)