The heel turn of WWE Champion CM Punk has been a topic of conversation backstage in WWE for the last couple of weeks. The company is aware of the lack of top heels and the feeling is that Punk's fans are going to be Punk's fans no matter what.
As for the execution of the turn, WWE knew it had to be against The Rock because given the split reactions drawn by John Cena, they wouldn't be able to get it over. The premise of Punk's turn is that he is upset he hasn't gotten the respect a champion deserves, not being featured in show main events. As one source told me, it's pretty much him playing the real-life story back into an angle.