This gets said on almost every pandora thread, but if you put a non-pandora charm on your bracelet, you can void any warranty for your bracelet you have in place.
Yes you can break your bracelet with a non-pandora bead because the fit / thread is not optimal. Your risk - but if your willing to do it, go for it. I saw a non-pandora bead get stuck on a pandora bracelet. Those bracelets are too expensive to risk it in my opinion - especially when you can get the real deal around 30 bucks or so.