A single actor controlling consensus is a successful attack on a DPoS blockchain. Essentially, any time we have a single actor controlling multiple top 20 witness nodes, we have an attack in progress. Once it reaches 11 nodes, the attack succeeds (I might be wrong about the number, it might be 13)
Pretty classic DPoS scenario, but we have to talk about it with strange vocabulary for reasons I don't quite understand :)
Basically, we can't determine who controls what accounts, and stake is all that matters in voting. The expected action from the attack is to fork out the tokens used in the attack. This was described way back in the early graphene days. Before protoshares was even live. Things are getting really muddled because of the emotional responses, twists in vocabulary, and the expected, messy cleanup that comes after the fork.
I think the weakness we're seeing now is that those who unwittingly participated in the attack and understand what they should do next time are in a very weak position to get their stake back. They don't start with any stake, and they've been vilified
*edit*
and yes, someone could buy enough hive to attack, but they should understand very clearly now that the money will be wasted. I suspect the rebranding on this fork was due to some complications with Steemit, Inc and exchanges. In the future, I expect we'll be able to "fork in place" and remove the attacking stake