It's not an issue with the amount of RAM but the way it's allocated, I think Bethesda have written up on it following its' issues with Skyrim, Fallout, et al.
I think cross game chat is a good feature, but I can also understand why Sony might not have seen the need for it when the online capabilities of the PlayStation were being explored. It's something that hadn't existed before (as far as i know) and that the Xbox 360 didn;t get it right until a few software updates after the launch.
Additionally as an Xbox and PS3 guy, it's something I don't make a lot of use of, I play with all my friends online in the same games at the same time, and when I'm not playing the same game as them it's our own private time, we use Facebook and texts to communicate.
I think it's one of those nice little bonus features, but that's just me.