@aphoria - the resale point is a very good one.

I see below that they are hung with Molly Bolts, a brand of drywall anchor. That's significantly different than a single screw.

If it's mounted with screws which are not in dry wall mounts (anchors) I have no idea why it has not fallen. It's hard to screw a drywall screw into just drywall without stripping out the hole. You sure there are no anchors?

The probability that at least most of the screws are hitting studs is 100%. Otherwise there would be a pile on the floor and 5 little holes in the wall.

@gregmac, very good point. I added the CO detector to my answer.