Over the weekend Party Poker dropped skins such as Empire Poker from its network. This has immediately reduced the number of players.

Bill Rini's blog explains what this means:

"...from a business standpoint, it's a mixed bag for Party. It was smart of them to get out from under the skin agreements they got themselves into when they were trying to fuel growth. The skins take a large cut of the rake and were killing Party's bottom line and most of them were turning a blind eye to affiliates who were offering rakeback which was luring away Party's best customers.
On the other hand, they nearly halved their customer base and now must fight with other sites like PokerStars and FullTilt to win the skin players who will likely be up for grabs. I also wouldn't be surprised to see shareholders filing class action suits against Party if the markets hammer the stock."

(via Bill Rini )