Who pays for this power usage?
Peercoin solves this issue
By replacing mining with proof-of-stake, only the votes of the wealthy nodes count.
I don't know about you, but I don't like to keep a lot of funds on a public mining node.
you dont have too keep all your funds there
How do you prove your stake without a private key?
if you have 100 coins, 10 on the mint address, 90 on a non mining address.
Perhaps I'm missing some detail of proof of stake, but doesn't it need 50% of coins to agree on the block? If everybody kept 9/10ths off their mining node, how would a block ever be created?