While consoles as a traditional have often been positioned horizontally as a rule, there have been numerous devices that have been able to work when positioned both horizontally and vertically. According to Microsoft, the Xbox One isn't such a device.
When speaking with GameSpot UK, Albert Panello from Microsoft's Xbox division warned gamers off storing their console vertically because unlike the Xbox 360, they didn't design the Xbox One that way.
"We don't support vertical orientation; do it at your own risk," said Panello. "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."
This isn't a huge issue, but sometimes vertical storage does make things much easier.