CM Punk and The Miz are, by all accounts, actually decent friends. The thing about The Miz is, he annoys everyone. Ricardo Rodriguez recently stated in a shoot interview that there wasn't a single member of the WWE roster that hadn't tried to fight Miz at some point. Punk's beef with Miz stems from the fact that The Miz was booked to face Cena in the main event of WrestleMania XXVII instead of him. Punk, who has called his WWE career a failure since he didn't close 'Mania, could not believe that he hadn't been given the spot instead and claimed that Miz should be nowhere near it. Punk elaborated on an episode of The Hot Clicks podcast in 2011, saying:
"Miz knows exactly how I feel. I've told him about it... I think Miz doesn't know how to deal with that. It's just my brutal honesty. I think you got to just let it roll off your back or you get confrontational about it"
Punk should have been in there with Cena instead of The Miz, that much is for sure. The WrestleMania XXVII main event was one of the biggest let downs in WWE history and Punk proved he could get the best out of Cena just a few months later. And yes: The Miz is REALLY annoying.
