When both candidates express a desire for follow-ups and rebuttals, you don't whine about the rules, you agree to it. Its been done in debates before, and no-one punishes you for changing the rules.
And considering how stupid the last two questions he picked were, they could have afforded to take the time.
But I wanted to know who was the bigger threat: A nuclear Iran or an unstable Pakistan? Also, Which is tastier: a big mac or a whopper? And finally sirs, a question of importance: Ginger or Mary Ann?
The reason Tom Brokaw was such a stickler for the rules is they were bad rules designed to create a safe debate for the two candidates. The two campaigns created the rules without Brokaw being allowed in the decision making. He was clearly bitter and it showed in him constantly reminding them "Your campaigns worked very hard on these rules."
The candidates decided they didn't want the discussion period or follow up questions because they wanted to just give speeches, not debate each other. Obviously the candidates realized throughout the debate the safe route wasn't what they wanted and I'm glad Brokaw did give them some leeway. Hopefully they'll open up the rules for the last debate and maybe actually debate each other, instead of stump on stage together.