Most are designed for the cover to move to the side when deployed but some are designed to split in some way that could cause the rhinestones to come free.
An airbag is just a carefuly sized explosion instead of a kevlar pillow case, in a crash the airbag is deployed in a fraction of a second, lots of engineering goes into making them safe. However, the rind sones aren't an intended part of the system and can be separated from the wheel and "knocked" out of the way at high speeds, much like ball barberings in a claymore.
Told a couple once "Just so you know, in an accident the clipboard you've got glued to your dashboard will hit you right in the face as the airbag explodes madam, so it might be a good idea to remove it."
She looked at me with huge eyes then turned to her husband who was looking straight ahead with an annoyed look on his face, they took off and the clipboard was still there on their next visit...
I'm one of those people that has never learned to drive and i know nothing about cars... I'm guessing from the comments that the joke here is that the stuff attached to the steering wheel will explode in the driver's face if the airbag is activated, is this right?
Rhinestones aren't really that sharp though (unless they're the really nice glass ones which I'm assuming these are not). It's also likely that at least the first two are plastic backed sheets. I can't imagine they'd be worse than the sharp metal logo usually on there.
Disclaimer: I know more about rhinestones than cars, which isn't a lot
Really all it's going to do is slap your hand with the bedazzled parts, I doubt there is enough energy to make them all fly unless they are pretty loose. But it would still hurt like hell cause I had a Toyota logo on the back of my hand after getting hit by the airbag in my car.