Last night my friends ps3 was stolen, and this mourning the thief logged on to his account. It says he's on line and at the main menu on mw3 is there anything we can do to track this guy?
Did he even call the police? In theory, all it would show is that the guy is logged on. The ISP would be the one's who would track where the IP address is coming from. The other thing is that with all the PS3's out there, Sony can't be in the position where they can act as law enforcement. And who's to say that somebody wouldn't try to take advantage of the system and say "that guy stole my PS3!" without any proof?
Also the thing you have to remember is that the guy who stole is probably not going to be the guy who's using it. Most stolen property is sold within 24 hours. Tell your friend to call the police and file a report. If he has any kind of insurance, he should also call and file a claim. That's all you can do.