Isn't limited by the game or your PS3, but by the number of servers... technically, it goes over 5,000. Technically... It's 5,000 concurrently logged in characters, per server, so there's even more different individuals you have the possibility of running into on your own server, and the duty finder allows you to play with players from all the servers on the same data center.

You're right though, unlimited is kind of a powerful word there X3