Had it been a big man hitting a guard like that, it would have been called.
I'm really on the fence about that play. At any other point in the game, it probably would have been called, and we'd all be fine with that. But on the last play of the game, do you want the refs making a call that essentially gives the Bulls the game (free throws pending)?
On the other hand, if Rondo is going to make such a dumb mistake at such a critical juncture, then his team has to pay the price. And if it costs them the game, then that's his fault.
I'm torn. But considering the fact that it was pretty clearly a flagrant foul, it's not good that it wasn't called. The NFL is on a crusade to take objectivity out of their officiating (got rid of the minor/major face mask distinction, got rid of the force out rule, etc.), and for good reason. The refs should just make the calls as they happen. Of course, the NBA is more subjective by nature, especially on foul calls. And if the League office reviews the play and hits Rondo with a flagrant, then they'd be admitting that the refs blew it and cost the Bulls the game, so don't expect that to happen.
It sucks for the Bulls, but I understand why the refs didn't call the flagrant.