This thread seems unclear to me. Are you talking about the Black Market AH or the normal AH? For black market ah it has already been said that it is considered a shady place and you can be ganked.
For regular ah one toon is rarely going to be very successful at this. A bank toon in its home cities doesn't have to flag pvp even on a pvp server is my understanding. So engaging them could be tricky.
So I am going with the idea that you are talking about Black Market.
in which case this quote applies:
Found here in full:It’s also worth noting that the Black Market Auction House has the potential to become a world PvP location for those on PvP realms. Just like the name implies, these are goods being sold out in shady locations away from the prying eyes of guards in the cities. They are not in neutral or safe zones. For PvE realms, it’s not going to have that same risk for placing a bid as on a PvP realm (aside from being outbid).
http://us.battle.net/wow/en/blog/617...daria-6_5_2012