I mine with slush, at mining.bitcoin.cz I am not at all disputing that 51% attack is one of the known attacks and that 51% of hash power concentrated in the ha

I mine with slush, at mining.bitcoin.cz I am not at all disputing that 51% attack is one of the known attacks and that 51% of hash power concentrated in the hands of any one actor is something to be prevented. I also dabble in alt-chains, and the Terracoin chain has often had 51-60% of the hash power in the Coinotron pool. It happened to GHash.io before, yes. I think they made it right. It's up to the rest of us to take our miners somewhere else to minimize the possibility of a rogue actor at GHash.io causing problems. As Coinotron once told me, a pool operator just runs a pool, can't control the users. There is no fair way to turn away hash power or "self-police" as a pool operator. I think if I read the graph correctly, the CDF provides a logarithmic probabilistic dis-incentive to be >50% of the hash power and also act fairly (in other words, to work on any broadcasted solved blocks that don't contain rewards belonging to you), so it will be interesting to see what happens next.