Apparently the PS3 version of the game is a bit buggy when it comes to multiplayer. It started with the fact that a large majority of game owners can’t even connect to the game servers to start a multiplayer online match.
The precious few who can still can’t do much as the bugs contained within online play mode. The company, Ubisoft, knows of the problem and wants everyone who is having problems to go to their forums and leave detailed complaints (when did a company start asking people to complain?).
The reason they are encouraging you to leave complaints is because if they are remotely intelligible and detailed enough, it will help them find the cause and either whip up a patch to fix the issues and push it out through the network or fix the games and begin shipping fixed copies. Until its fixed though, I’d probably recommend just playing on your own and honing your skills and scoping out the maps, but it looks like fun once they do get things working again.