You'll find alot fo the dealers have them on the shelves used for warranty reasons (people complain they're marred, colors don't match etc...).
Nissan never asked for them back and you CAN NOT throw a unexploded air bag away...
They have a kit to detonate them and everytime we had some we were going to blow up the dealership stopped for about an hour to come watch.
We'd put them in dumpsters and blow the lids clean off, we put trash cans over the top of them and blew them 15' feet in the air. It was great :rofl: