We've had a couple of early reports of Steam Machine failures, describing a red light indicator of a problem that means the PC won't turn on, which is something that'll be very familiar to those who've had an Xbox in the past.
A Redditor posted (see below) that their "Steam Machine was pretty cool for the 20 minutes that it worked", detailing how things went wrong, and how the PC ended up displaying a 'Red Line of Death' and not booting – reminiscent of the 'Red Ring of Death' visited upon some unfortunate Xbox 360 owners (myself included).