Trying to find someone with an IP address?

[Samantha..:*]

I recently received a really mean anonymous message on my blog. I WAS able to get an IP address from a person who was visiting the page at the same time and has come back numerous times since. All I can do with that IP though is track it back to the city, and it is the same city I live in. I have a good idea of a few people it might be, only problem is all I have is an IP and I can't do anything but find the city, service provider, and type of computer they were using, which is no help.
Is it possible to get an IP address from someone else's facebook, twitter or tumblr and see if it matches the one I have? I just want to ask them to please stop, I know I can block them but I did that once and it didn't work, if I can actually tell them I know it's them they will stop, but I have to be sure it's them first or I'll just be opening a can of worms.
Yes, I know you can't find an address from an IP, but can you get an IP from facebook or twitter and see if it matches?

[Chris G]

The only way to get the identity of the person from their IP address is to get it from their ISP.  The only way to convince an ISP to divulge that information is with a court order.