I dunno. I'm not sure I'd like to see smoking bugs on my floor during the summer. Also having their wings float in a breeze every time the doors open would be annoying. I would think it would be fun as hell though to use outside!
"Quick! Blast them before they get into the building!" *poorly voiced Star Wars effect sounds"
I can only think it "cruel" because you're frying the suckers in mid air. That just sucks... It's not much different then a bug zapper though. Only one being with the laser, they don't really see it coming, and with the zapper, well... It's not my fault they can't see something wrong with oddly colored light...