There used to be a FoldingAtHome application for the Playstation 3 that I ran for a while. It's a shame it never made its way to other consoles because they're properly underutilised during the day, for me at least.
It wasn't great though - it didn't use spare cycles. It had to be started and run exclusively.
If they baked it in to use cycles when games were paused for instance or made it switch to FAH instead of powering off, it could have been so much more.
I like how you leave room for the possibility that there is a significant percentage of people playing on their consoles for the vast majority of their waking hours :-)
If they baked it in to use cycles when games were paused for instance or made it switch to FAH instead of powering off, it could have been so much more.