[GoLightly]

Your ISP would require a subpoena to release that information. They do not give out the identity of their customers willy nilly.

[Repub4bush]

No they don't give them out, but they are very easy to obtain for someone who knows the in's of the Internet. Most forum mods have access to them, as well as some chat servers such as mirc.
I realize this didn't happen in this case, but I know it can be done effortlessly by Internet techies.