You know... Really, most PSN games are p2p in the sense that its not an official server we play on. Warhawk, GTAIV, Killzone 2, Resistance 2, Unreal Tournament III, etc, are all run on everyday connections for gameplay and the "Official servers" only collect stats from the host after a round. EDIT: Okay... maybe not all of those (or any... :lol
... I think KZ2 actually runs on "official servers" since anyone can host any number of players (I think...). Maybe you should forget that I wrote/you read this paragraph.
Still, I read they said it's because everything is fully destructible and they have to send all that info as well. Meh... whatever... I'd be interested in seeing a bandwidth report from someone that hosts a 4 player game to see just how throughput is needed for what it's doing now.
Even if it does/can max out a moderate connection, I don't see why they couldn't write in a bandwidth checker that would adjust the amount of channels based on the person with the lowest bandwidth. Or possibly make a "Push to Talk" system that would only allow two people to talk at one time (so if 3/4 people were pushing to talk at once, it would only transmit the first two people that pushed).
Also... what is it? They blame it on the PS3 firmware, then they say they "had 4 player voice chat working fine, but had to take it out because it can cause drops with lower bandwidth connections". So is it the OS or a connection problem? Maybe a connection problem based on OS limitations...