What's interesting is that this is nothing new. I wouldn't be surprised if there is a nano-ITX motherboard in there made entirely by Intel. There have been nano-ITX motherboards available from VIA and others for some time now (check out
http://www.mini-itx.com for more info), and that's not even including the mini-ITX motherboards that have been around even longer.
Of course, I personally think most of those PC mini-boards were inspired by the predecessor of the Mac mini: the G4 Cube. So in that respect, it's business as usual in the Wintel world.