Pretty clever use of game mechanics I saw last night. Theres a few methods in here.
If you are in a bidding war for a BMAH, you know how quickly you can run out of gold and have to go to the mailbox to get your outbidded gold. What a guy from Blood Legion did last night was pretty hilarious.
Do the usual low timer bidding war, 1-3 minutes before ending time, and ask a few of your friends or guildmates to head to the nearest mailbox to the AH and mount up on tundra mammoths. 3-4 of them will do just fine, and the person in the bidding war will never expect it and waste (hopefully) enough time to let the auction end. If they are smart or have dealt with blockers before, they could zoom in and try to click the mailbox from first person view, but that is still wasting time.
You could also just straight up bribe them with "ill give you 50K to stop bidding on the item". Open trade with the person, tell him after it expires that you will pay him. Let the auction end and just walk away. This can also work the other way around, have someone in your guiild that is a similar class that can also use the gear to tell them "ill stop bidding for 50K", tell him they MUST keep the trade window open until the auction expires, preferably out of range of the auctioneer. During this time the in game player can tell you when the auction has X time left, log over, bid before the person with trade open can react. this usually requires that the bid be over half the max gold limit for characters, forcing the player to react, get to mailbox, withdrawal, and re-bid in time.
The other method is just to have a friend or guildmate target the person you are bidding against and spam an open trade macro on the player constantly so he has a hard time opening the AH window.
Each of these has shown success for me (or the other player ) so far. I should get back to work now, hope its all clear as mud for you! happy bidding!