[GordonS]

Think of bank accounts that don't allow instant access to your cash, where you gave to keep it in for a year or whatever to get your interest.

With PoS, the more coins you tie up, the more chance you have of 'winning'.

That's my understanding anyway - someone more knowledgeable, please feel free to correct me!

[ufo]

The problem is in the details: how do you use this to reach consensus? How do you agree on a randomness source to picks the "winners"? How do you prevent people from mining multiple parallel histories, devolving the system into proof of work?