Seriously, though, you can hurt your shoulder if you try using your elbows to land with... I've used them enough for that purpose to discover that that is very bad and you should use your entire arm. Just a don't-want-to-be-prone instinct, I guess.
James, do you mean thicker mats like the ones about 2 inches tall? We have some of those and some thin ones (not quite an inch tall) and I don't see how you could catch a toe in the thin ones.