Ackman may have pulled all his buddies into the act, promising to cooperate with them on a future target. This appears to be a purposeful attempt to destroy JCP, perhaps so Ackman can say that he was right about Ullman and the other changes he supported. He certainly has the motive.
If this is the way of the future, there's no company they can't take down when they want. What a way to make money.
Where and when will it stop? Maybe a few unaligned hedge funds will step in, including Icahn, who has no love for Ackman.