Besides, nobody is really supposed to be wandering around near a forest fire. If they happen to be there, I say "fair game" -- I'll even pay $10 for an ear.
If you -as all projectile-weapon-wielding hunters should be- are aware of what is downrange, then shooting at things in flight with a shotgun is a relatively low risk activity.
A few bits of stray shot travelling at terminal velocity are unlikely to do significant lasting harm to someone on the ground. (For comparison, try to find out how many folks have had fatal encounters with pellet or BB guns. The size and weight of an average BB is in the same ballpark as a single piece of shot.)
I was thinking of regular shot (20/12/10 gauge), not bird shot. I have a skeet shooting mentality. I imagine you all are correct and bird shot would not be carrying deadly velocity when it returns to ground level.
Anyone who's been to skeet, pigeon or water bird shoot can tell you that, you only really notice it when you hear it hit your hat / jacket it sounds like rain more than anything else.
A bullet needs to be fairly heavy to actually kill you, even 72grn bullets are not heavy enough to do serious damage, they will hurt tho...