Okay, you prolly experienced yourself, finding some nice Epixx like KROL BLADE, but some dude put it on AH for 580G bid and 650G buyout... but you wanna sell yours asap. Put that auctioneer on your friendlist and as soon as he comes online, log to your scam char, and whipser him, you wanna buy it for 635G... and he should send it with post. The item will be 2 days on your mail box and wont influence your item in the AH!
Protecting yourself from this: always tell the dude asking for such stuff, he should buy it and he will receive the difference. Works perfectly and with rare items and Librams.