I think you mean, have you fallen with clipless pedals and not been able to release (or forget to) in time. If someone rides enough, they will fall, but often it isn't much of a fall, and if you release, it is no different than any other time you fall.

So, I would say I have never fallen with clipless pedals - which is odd since I am normally not all that co-ordinated. Perhaps it is because most of my riding was done on private trails where there where no bystanders. From reading these threads, it seems to me bystanders are a requirement.