Why would you want to put all those CPU's in a pen when they'd be far happier out in the wild?  Is there any difference between 100 computers run by 100 interested people or 100 computers run by 1 interested person?  99 people, that's the difference.  Bitcoin does show us the future.  It's a black-hole of computation and eventually it'll implode.  Want mass adoption?  I say limit all mining to Androids, period.  It's kind of oxymoronic really, a centralized distributed network.