Is Uncharted 2 pushing your PS3 hard? Probably.
Did your machine lock up while it was being pushed hard? I completely believe your account of what happened, so yes.
Did your machine lock up because there is a memory leak, bug, etc. in Uncharted 2 or a system library call that Uncharted 2 uses? Possibly.
Does your machine locking up while being pushed hard mean that the PS3 will be destroyed? It's theoretically possible, but unlikely. I know of about 3 instances over the past 30 years where software being developed by the team I was on actually fried hardware, and that was always due to some sort of glitch in the way the hardware was designed. It's just very rare for this scenario to exist.
So, while your machine locking up while it was being pushed hard seemed to indicate that the machine was being overstressed, this is not very probable... likely the two effects are separate and not related to each other. Welcome to the world of coincidence.
John is over 30. John has brown hair. All men over 30 have brown hair... BZZZTTT! 
