That's right, the Xbox One wasn't designed with vertical orientation in mind according to Albert Panello, senior director of product management and planning at Xbox.
What he actually said, was "We don't support vertical orientation; do it at your own risk. It wouldn't be a cooling problem, we just didn't design the drive for vertical. Because it's a slot loading drive, we just didn't design it for both".
Curiously though, Panello also stated that "we found, interestingly enough, that 80 percent of people, believe it or not, have their Xbox  horizontally".
That sounds a bit steep to us... Which way do you guys have your 360s?