Or else it's because the commercial short:long ratio is 2:1, which means there are is a relatively large speculative long position.  Yesterday being options expiry on the Comex, and with gold having stayed relatively strong into options expiry, a bunch of long, in-the-money options would have converted to futures positions.  So having a big drop today puts huge margin pressure on those new positions, forcing liquidation of the long-side contracts.  Usually the big move is done before options expiry, to either get the long-side option holders to liquidate or to have their options expire worthless.  However, this move works just as well - whatever it takes to game the paper market.  This is what you can do if you're a bullion bank backed by the FED with infintely deep pockets.  Enjoy...