Don't buy an aluminum mountain bike with a non-replaceable derailleur hanger

Last October, I crashed on the derailleur side of my (old, low-end) mountain bike, landing on the rear derailleur. This bent the (replaceable) derailleur. It also bent the (aluminum, non-replaceable) derailleur hanger. Which means the frame was almost totaled. (Not quite, because it's still usable as a singlespeed.)

Don't make this mistake. Mountain bikes crash. Derailleurs and hangers bend. It's expected to have to replace a derailleur and a hanger if this happens. It's not okay to have to replace the whole frame. If you're shopping for a mountain bike, either pick a steel one (because bent steel can be safely bent back), or pick an aluminum one with a replaceable derailleur hanger.

(My replacement bike is a 1996 Specialized Ground Control A1 Aim. Most of the bike is aluminum, but the rear triangle is steel. So it pretty much nails this one requirement.)