Of course mag will burn, but not under normal bicycle usage. In fact, often racecar suspension pieces (uprights) are made of mag and the brake calipers are bolted to them. Naturally, brakes get pretty damned hot. There are never mag fires due to brake heat. If it can life through that, then it can live through anything we're likely to put it through. The discussion is about whether it's mechanical properties lend it to being a good bike frame material. Frankly, it seems like a little more trouble than it's worth. Between Carbon, Steel, AL and Ti, I think we're pretty well covered.