Bunny hopping, an invention of the BMX'rs, is generally done with platforms by them and stunt riders like No-way Ray (Hans). The technique is different, requiring the toes pointed down and pressure applied slightly to the rear.

I prefer doing it with cleats as I don't want to get that high just to jump mud puddles. I prefer the equally valid technique of pulling my legs up. That approach was very nicely described in a recent issue of Mountain Bike Action.
Al