Difficulty made a very weird jump. It went from 642.97400619 to 160.something (estimate was about 360) to exactly 642.97400619 again. 
Every 720 blocks the difficulty changes. So it will be most profitable to mine the 720 easy blocks, but your payout will be slow as it takes 720 blocks to mature.
So the miners will need to put some hash to it also at the high diff blocks to get their payout. This ensures that miners wont be dumping, but selling of slowly (if they sell, i think alot just hold).
Just another genious thing about this coin.
