Looking at so many posts from the PS3 community, I have to wonder if there is any correlation here at all.
a quick Google Search seems to indicate that hundreds of PS3's are failing while playing MW2 Online.

I read a few and there is nothing that can be attributed to one thing, but could this be video related?
While Activision and Infinity Ward did very well to make this game shine and really push the limitations of the Nvidia GPU, could they be pushing it to overheating?

Talk about it in the forums.