An investigation is in progress.
It seems that 343 Industries automated Banhammer process has a bit of an itchy trigger finger as they are currently fielding multiple reports of players being permanently banned from playing Halo 4 online, a punishment usually reserved for the worst of cheaters.
Most of these bans appear to be some sort of a mistake, with most of the affected players being banned after playing one of the new Crimson Map Pack maps. 343 Industries posted this comment on their official forums today:
We are not permanently banning players for previewing or purchasing the Crimson Map Pack. We are currently investigating the recent reports of permanent matchmaking bans.
We will provide further updates tomorrow. Thank you for your patience.
For updates, keep an eye on the official thread:https://forums.halowaypoint.com/yaf_postst135680_The-Official-Halo-4-Ban-Thread.aspx
Let’s hope this works out for everyone was was affected, as 343 Industries, and Microsoft, usually take a very hard stance on bans stating that: “Our automated system builds up a digital case of wrongdoing before any ban is enacted. If you accidentally disconnect a time or two, you won’t get banned. Instead the system looks for patterns that can’t happen accidentally. If the banhammer detects enough wrongdoing, you were doing wrong. Case closed.”
It seems to me like your automated system needs at least some small measure of manual error checking, before taking such a drastic measure as a permanent ban. We will update this post as more information becomes available.