Rooney started falling before any contact, that was clear. He definitely sold it to the ref.
Almunia should have seen that rooney was never going to score, and should have pulled his hands back. Unfortunately, by rushing out, he made it very easy for Rooney to win a penalty that probably looked nailed-on to the ref. And let's face it, that would be a penalty for 90% of refs. Definite contact, despite the fact that Rooney wouldn't have come close to scoring had Almunia been a little smarter.
Fred-I don't watch Arsenal nearly as much as you do, but aren't you being a little harsh on Denilson and Diaby? They didn't do too bad a job today against manu's midfield, did they? The OG was pretty bad though, but Diaby made a couple of runs that created some space/chances