The IP address will tell you whose Internet services were used to connect to the web site. That will rarely point to an idividual user. Of course to use STDg's example Tiscalli, may well know who was using a particular IP address at a givin time but that is not the sort of information I would expect them to be divulging to web sites.

On top of that, there are public machines, shared IP addresses, some may use a proxy, etc.

As far as I'm concerned, knowing an IP address is just one tool that can help give in idea of who is posting and as I said in my previous post (which I forgot to sign) it is my believe that people here will know what is going on far more often than they don't.