I've recently been interested in the subject of unanticipated or unintended consequences. Most of my interest has been fueled by a sense that arguments of the "nobody could have predicted this massive, now-obvious consequence of actions I took" type are becoming more popular: think how often they've been deployed in the aftermath of the Iraq war, the financial meltdown, Deepwater Horizon, etc..
Of course, unanticipated consequences can be good things too, as I noticed this morning. We recently bought a new vacuum cleaner, one of the bagless cyclonic kinds with the transparent canister. I mainly liked the fact that there were no bags, and that it was less than 20 years old. But my kids turn out to really like too: so much so, in fact, that they're actually cleaning their rooms when friends come over.
Why? Because as they vacuum their rooms, the canister turns into a "tornado of grossness," as one of my son's friends put it.
Making the canister transparent turns vacuuming into entertainment-- and because it combines technology, loud noises, visual effects, and gross stuff, it's irresistable to young boys.
I have no idea if the designers have kids, but: well done.