But failures don't always go for a 23-mile joy-ride into restricted airspace. That's kinda cool.

As to damage, given the size, probably not a whole lot if it just died and fell. Might kill someone who's incredibly unlucky. But consider if it flew around at a really low altitude: power lines, people, windows, all in range of the blades. Given that it went 23 miles on its own, having working ground-avoidance software isn't an unreasonable assumption.