I should clarify what I mean by this. Dash's Evolution proposes a feature where a N-of-M quorum of master nodes can instantly confirm a transaction by sending their signed confirmations to the block chain. This quorum M is chosen by using historical block chain hashes (well it was current block chain hash until I pointed out to Evan that was insecure in this Altcoin Discussion forum, and so I assume he changed his design after Illodin pointed out the improvement).
So the theory is that even if there are orphaned chains, they won't disagree (conflict) on these quorum announcements. I pointed out to Evan that if he changes the quorums on every block then there will surely be conflicts. So again I assume he altered his design to not change the quorums very frequently, thus thinking he had fixed the problem. I decided to sheepishly be silent and let him go down that direction, knowing full well that it is flawed.
Isn't it much worse than that? If I own a majority of masternodes, I can have my faulty nodes agree to confirm transaction A, dump all their votes of the their mempools and then confirm a double spend B with another merchant. None of the votes will get baked into the blockchain by that point if I'm quick enough.
This turns the cost of a double spend under instant X into a constant proportional to the amount of locked collateral I have, which is far worse security than regular POW, which is super linear in the number of blocks.