In my original post I give an example of why that's not true. The same guy can own all the big PoW hashing pools in secrecy, which is a sybil attack, not collusion. He can operate profitably the entire time and initiate the long con or other strategy whenever he wants.
The only thing he needs to do is to buy all that mining hardware.... Oh, and to produce some blocks... the cost of which is superlinear in the number of blocks... Mmmm....
No there is a social engineering attack at work. r0ach wants to rename it as a sybil attack, which isn't entirely wrong since the social engineering attack does use a sybil technique.
By making pools appear smaller they encourage independent miners to (continue to) send hash rate there. Thus the evil pool operator doesn't need buy the hash rate himself, he's tricking miners into letting him use it.
Without the social engineering component the pool sybil attack doesn't really do anything. Split a 50% pool into five 10% pools and you still only have 50%.