There are much easier ways to find out quite a lot of info about people without using their IP to do it - the average user drops a suprising amount of publicly available information as they go around the internet - often just from a username and a bit of detective work you can find someones full details in a couple of hours.
Over on the overclockers forums in the past they've been able to find out a rather shocking amount of people, in one of the threads one guy even boasted about how secure he was online and dared anyone to find his real info... which I did in <30minutes even tho he'd done a good job of hiding his details online I found an obscure reference that I was able to link to his steam profile and from there his hometown and a clue to his last name, bit of digging later and I had him narrowed down to 1 of 2 addresses - which I didn't post publicly but he did confirm that one of them was correct in PM... if I'd been seriously trying to find him a phone call or a bit of stalking would have done the rest.
Edited by deleted (Tue 22-Nov-11 19:29:04)