They wanted their fair share. Each would accuse the other of greed. The judge sided with the ad agency and Dahl had to write a six-figure check. Once good friends with them, Dahl won't have anything more to do with Coakley or Heagerty. Gary got rich quick and then he wanted more than he deserved.
Dahl explains it differently.
The same people who were so enthusiastic about helping me get this thing off the ground got greedy. It was not pleasant and it didn't leave it with a happy ending. That's the reality of the whole thing. There was a dark side to it, too. Coakley went on to become an advertising professor at San Jose State University, partly because of the Pet Rock mystique.