I spoke briefly with HBO Prez Ross Greenberg at the Mayweather-Hatton Press Conference the other day and he said that the main issue in reaching a deal with the UFC is Dana White's insistence on using his own handpicked shills of Rogan and Co. for the announcing team. HBO wants to use their own broadcast team, because they believe there should be some level of objectivity involved.
Or maybe, just maybe, Ross doesn't want to hear the term 'Heavy Hands' ever again.