Most roads are crowned. When on such a road, you might find it helpful to unclip the foot that is on the high side of the road (towards the center of the road, usually going to be the left foot in the US). Of course, if you happen to lean away from the unclipped foot, this just guarantees a longer fall.

Frankly, I don't actually get the whole falling down because one didn't unclip. Maybe it's the added leverage of my size 51 feet, but I can always unclip before I go down. Well, except for that one time back in 1982 with the Cinelli M71 clipless pedals that had the little button one had to push to release the cleat from the pedal.

SPEEDPLAY : HIGH PERFORMANCE PEDALS