If it's a static (dedicated) IP you could find out which part of the world the server is located at, possibly get a name and town, state but that's about it. If it's a dynamic IP you won't be able to tell a thing about the user because a different user will have it at any given time. AOL, PeoplePC, Netzero, etc. all use dynamic IP's and of course if someone is using a proxy or an anonymizer then the IP tells you nothing but where the server is located.

Why all the concern?

Shade