Originally Posted by
ThermionicScott
You're not crazy; I remember reading Sheldon (or maybe Jobst Brandt) saying that the only purpose of the cap was to keep from poking a hole in the tube while it was rolled up.
I no longer throw away valve caps, though -- I patched up a bunch of old tubes a year or two ago and wasn't able to roll them up properly since I was short on caps. 
I fold my tubes from opposite the valve. Valve is last and lays on the rolled tube. Held in place by the elastic. Haven't punctured a tube yet in many years. (I sometimes have to roll twice to get the valve to lie on the tube, not be at the folds.)