Correct me if I'm wrong, but isn't there a rule that says if a pass comes within so many yards of an eligible receiver, it's not considered "intentional grounding"? If so, one could probably make the argument that when a QB spikes the ball, it usually comes down within the range of several eligible receivers, including one or both tight ends and probably a running back also, therefore making it a legal pass and not "intentional grounding." I'd always just kinda assumed that was the case, but I've never looked into it to find out.
It could also be one of those weird exception rules like they have for FG-holders... if the ball carrier's knee is on the ground, he's down UNLESS he's the holder on a field-goal play, in which case it's all cool, man. I seem to recall a thread question on that a few weeks ago when Shark ran in the fake field goal, and somebody on here found the actual rule covering that.
Is there another such rule that covers spiking the ball?