For sure the number of players is too high for the ps3 memory, but it´s not the only reason about lags, cause during the beta 3 i made some ALEAS with 40-50 players around me and i never had any lags issues.

Right now when i'm playing on maps with few players compared to other maps like coerthas, i've always got lags issues and since the last update from SE I also have tremendous lags during dungeon, last time i played during 30min whithout seeing any members of my team...
This iś not only a ps3/ISP/ issue, the problem mostly come from SE servers and the fact that they authorize more players to play on a server than it can support. They open a large number of new servers in US and Japan, but the worlds transfers are not ready yet, so players with high lvl caracters don't want to create a new caracter and start again from the begining...
Maybe in a few months we should see the end of the tunnel...