Some rather unsavory people are taking advantage of the fact that every Xbox One can be used in developer mode, and they're using it to trick people into essentially bricking their consoles.
They're doing this by telling people that they can enable backwards compatibility on their console, by unlocking developer mode, changing the sandbox ID to [REDACTED] and then then restarting their console. This will NOT enable you to play Xbox 360 games on your Xbox One, but it WILL cause your console to be stuck in an endless boot cycle, and be rendered inoperable.
MS has been pretty good about taking care of people who have issues with their Xbox One so far. I have to wonder how they're going to handle people gullible enough to try this. If I had seen this floating around without warning, I would never have believed it was a way to enable backwards compatablity. On the other hand, I wouldn't have believed that doing something in dev mode would ruin your entire console either.