I actually think Rondo's matador tendencies - to an extent - are condoned by the coaches. Doc has said in the past that one of the weaknesses of the defense is that it doesn't force very many turnovers. Allowing Rondo to gamble might be an attempt to compensate a little bit for that, although judging by Doc's reactions in timeouts, Rondo does it a lot more than he wants.
Personally, I'd prefer if Rondo just stayed in front of his man. Every one of our starters is capable of defense ranging from solid to exceptional. I thought one of the best aspects of our defense last year was our propensity to force 24-second violations, which seemed to happen regularly. This year, and especially lately, that just doesn't happen anymore. I forget who mentioned this during last night's broadcast (it might have been Thibodeau, actually), but somebody said that the team has lost track of the fact that they're a defensive team first. I hope they get back to that as the playoffs begin.