My SPDs don't pop out, though some people seem to have problem with this. With SPDs, I've noticed than an upward pull combined with inversion of the foot will cause them to suddenly pop out. I don't know if its a design flaw or a safety feature, but I accidentally unclipped a few times until I learned not to do that when hammering or attempting to slow down and it hasen't happened since, even with the tension set relatively low. I currently use a variety of SPDs (mnt) and Look Keo Max (road). Look Keo pedals are excellent and less prone to pop out with sloppy pedaling. I have also used crank brothers pedals...never had a problem with those popping out either, but I dislike them for other reasons. Many people rave about Atacs, but I've never tried those.