Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
When the news broke about it being impossible to use Linux as a screen name on the Xbox 360 it sounded like such a Microsoft thing to do. Alas, the real reason why you can't use Linux as a screen name is much more mundane.
The news that you couldn't use, oh say, "Linux Rules" as a screen name on the Xbox 360 online gaming circuit appears to have first appeared on Xbox Scene News. After that, the story spread like wildfire as Xbox 360 users tried it for themselves. Their attempts were met by the error message "Your motto contains inappropriate language. Please try again".
A little more snooping by Xbox Scene News readers found that variations on the Linux theme, such as L inux, Lin ux, and L I N U X also failed to pass muster with Microsoft. Along the way, they also found that Unix and Windows wouldn't work in screen names either.
There was the clue that led your ace reporter to call Microsoft's public relations and ask, "Do you block screen names with trademarks in them." The answer? "Yes, online Xbox 360 Gamertags [aka screen names] may not include trademarked words or phrases."