I keep reading here the same complaints. Cant support more than 32 players. Cant support super large maps and terrain. We've been playing that way in Tribes world since 1997.
Playing a game of Tribes with more than 32 players would usually dissolve into chaos. Optimally, the game is played with 12, 16 or 20 players.
Aside from that, keep in mind the obvious demand that Unreal 3's graphics place on bandwidth and overall performance. If there were more than 32 players in an Unreal 3 game, I'm sure the amount of lag, both net-related and hardware-related, would be significant.