I have seen a number of bows ruined in my shop by a belt sander, ruined a few myself when I first started out.
The key to using a belt sander is knowing when to stop using it. I narrow tips, flatten sides, flatten overlays, handle add ons, true up side bulges in the limbs and a host of other jobs. I never tiller, be it floor or long or short string, aggressively shape handles or fades, work on the back(unless I am flattening for bamboo) or work tip overlays to their final shape.
The biggest mistake I make with my belt sander is daydreaming and getting my knuckle into the belt, done it way too many times. Just finished healing up from my last encounter with a 36 grit belt, it takes over a month to heal because the skin and flesh are GONE..