I tend towards the theory that POS is more centralizing than POW, and the question is will it stay decentralized or end up with one address (or rather one entity) controlling 50%?<p>With POW a miner needs to continually provide new investments to be competitive, with new and more effective hardware and electricity.<p>But with POS you can just keep your coins in one place, and it will keep building up with no new investments at all (except running a node, a relatively small cost).<p>And in POS if someone ever reaches 50%, then it can forever hold that position, and it's essentially game over (baring a drastic hard fork).<p>It doesn't seem that unlikely that one big exchange will accomplish it.