Don't take the bait of the 'AH ban'. This has been discussed in the past, it adds nothing new and just causes folks like you to rebuke their bs. Just report them next time.
Originally Posted by beatific
In reference to the posts from several months past about bans for AH manipulation. GM policies may have changed but it is definitely possible to be banned for "aggressive AH economy manipulation." Several members of the US-Kel'Thuzad Horde guild Ministry were banned for that same reason. This was in classic in the days prior to actual guild banks and a few key members were in charge of the guilds gold and mats store and were aggressively controlling the AH for extended periods of time.
Emphasis added. I don't expect the GMs to hit you with a banstick if you're operating alone, unless you manage to, on your very own, become an actor of such weight that you can single-handedly control an entire portion of the market. In the example you gave, it was an entire guild doing so. Also, I'd add that there is the "grievance factor" to take into consideration: in your example, one could easily argue that what Ministry's members were doing was pure grieving. On the other hand, one person playing on one specific item for a short period of time wouldn't risk that. Typically, I've been buying off all the illusion dust on the AH for the past two weeks and reselling it at 10g/dust. I've made a nice bit of coin, and now that other players have barged in on my niche, I'll be moving on to another one, no GM action required.
In short: unless you really, really go out of your way to mess with people's AH life, I can see NO reason - and have never seen any examples for that matter - to get banned by a GM.