Here's the thing people need to take into consideration.
Playstation All-Stars is like, Playstation's big name thing right now in terms of exclusives. Yeah it doesn't sound like it with whining fan addicts but lets get past that and say that this is pretty much the equivalent of the 'hype' for Super Smash Bros in the Sony area.
I'm not saying they're similar games, I'm saying that the fan support is pretty dang large.
When the original beta was going, they had what, 1000, 2000 people?
With the open beta they are probably having to support nearly a million. If not tens of thousands. Its possible that the servers simply crashed with the amount of overwhelming pressure that they didn't expect.