OK, since Im the first one to answer 'yes' i'll put my comments here...
Stopped at a light, traffic all around, light turns green, cars start to go but then stop again because left-turners are still in the intersection. I stop, car behind me doesnt. bonk.
I think 'sh!t', then i hear the engine behind me race.
I think 'sh!t, this guy is
trying to kill me.
I was already in gear and ready to go so i romp on the gas and get rolling. BONK (again)
but since i was going i wobble a bit but dont fall.
Get stopped. the woman says 'O My Gawd, i mean to hit the brakes and hit the gas instead :

'
I shoulda gone Yates on her a$$. [smiley=laugh.gif]
not exactly your scenario, but close enough.
the quicker reaction time could have made the difference between being sore the next day or squished.
I think being in gear and watching boils down to is 2 things
-decreased reaction time if you need to get moving (i think there are usually squealing tires before rear-end accidents)....kinda like covering the brake in traffic
-the other thing is attention level. if you switch off your riders-brain when you are stopped, you are less prepared to anticpate and avoid stupid stuff people around you do.