Shuhei Yoshida, president of Sony Worldwide Studios has stated that Cross-game chat will not be a feature that the PS3 will be able to support. According to Yoshida:
Once a game gets RAM we never give it back, it’s not possible to retrofit something like that after the fact… The game has to use its own memory to do [in-game voice chat]. There’s always voice chat in the game. But it’s a part of a game feature. It’s not a part of an OS feature. That’s the reason in terms of the ability to have voice chat across different games.
Therefore almost all of the PS3′s RAM is used in running software, meaning that no RAM is available to the console to run outside programs or services.