These exploiters are easy to spot in trade chat or Yell;
"WTS 20x[Queen's Garnet] 60k"
By the end of the day it will say 55k, 50k, 45k/stack and so on.
They keep selling huge amounts of Queen's garnet all day long with an unlimited stock, ruining the server economy every second someone buys the gems from them. The gems can and will be removed from the game by Blizzard, so DO NOT buy these gems.
Proof : http://img21.imageshack.us/img21/1024/duplicateexploit.png