It's people that are dumb enough to plug it directly in the wall and having it sit vertically is when they start getting problems. At least that's what Microsoft tends to think.
Well since the PS3 and Wii have a massively lower failure rate, then the logical conclusion to what you're saying is that all the dumb people are buying X360's and the smart people are buying PS3's and Wii's. Hmm.. you may be right.