my addition to this thread...
That one is very cool, but unlike the other two, it's actually a guy lipsynching to an a capella track by a group called Moosebutter (I thought those timbres sounded too different to be one voice, and indeed so). He explains this in the sidebar, so at least he's upfront about it. Moosebutter (whoever they are--an a capella comedy group from Utah, apparently) seem to know about the video, and supposedly helped him make it. It is funnier with that guy's facial expressions than it probably would have been without, so I'm glad I saw the video.
The Francois Macre one, by contrast, is actually one guy multitracking his voice, which is pretty impressive. You're right that his impression of Michael Jackson's vocals is a little wierd, though.
As a choir boy, I think I like the first one (Perpetuum Jazzile) best, because there's something about assembling a group of people and coordinating them in this way that's just really neat. Multitracking does give a better blend, however, since for obvious reasons, it's easy to blend with yourself.
Cool finds, everyone. This makes me think that we will never have a future quite so extreme as Wall-E, thank goodness, where people just veg out all the time. They may not be as productive in the conventional sense, if things are automated for them, but I think people are naturally industrious to alleviate boredom. Left to their own devices, there will hopefully always be people who make little random things like this.