http://www.eurogamer.net/articles/2011-08-19-why-the-ps3-cant-do-cross-game-voice-chatCross-game voice chat is not possible on the PlayStation 3 because of memory restrictions, Sony has revealed.
"Once a game gets RAM we never give it back," he said. "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."