yeah, due to the lighter-weight, a bicycle will get tweaked from equilibrium by a falling rider. However, if you've ever hopped off cleanly, like grabbing an overhead branch, or hopping straight up and off the back, the bike will continue in a straight line. Until it slows down enough to lean to one side, in which case it will carve tighter and tighter turn and lean more and more until it lands on the ground. BTW, I don't recommend anyone dismounting at 50mph to test this...