I figured this one out when I was bored.
What it does - You can put up a fake item on any AH and have players buy the item. You also get the gold when they buy the item but to them the item will be invalid when they go to pick it up from the mail box. At the same time that you put the item o the AH you get the disenchanted shard from it.
How to- (YOU NEED TO BE AN ENCHANTER-duh)
1. Goto AH
2. Put the item you want to disenchant & sell in the auction slot
3. Set the price and time
4. Click the disenchant button and make sure your cursor gets highlighted blue.
5. Heres the tricky part- start disenchanting- you should see the bar moving. (You need perfect timing) Right when the item is about to be disenchanted(when the bar is just about full) - HIT create auction at the SAME TIME.
6. if you timed it right the item will go on the AH and you get a shard from it too. MAKE SURE YOU LOOT THE SHARD RIGHT AWAY.
A good use for it is if you get a lot of BOE epics , you can sell the epic and get a nexus crystal. so you get money and a crystal from one item