Personally I think that they engineered gold to fall significantly
before QE3, so as to take some steam away from it.
For them it is better that gold go from 1500+ to 2000 after QE3, rather than from 1700 to maybe 2500 or higher.
It probably relates to some BS key resistance levels on charts and all that
Edit: Also, consider that gold as an investment is looked at on a 'annual' growth basis. Eg, if gold goes to $2000oz, that is up how much from January? But if it goes to $2500 it is up significantly more.
The higher gold goes in consecutive calendar years, the more attractive it looks as an investment to others, particularly for longer term investors who expect to see gains, and consistency. So I would argue that the Fed tries to break that attractiveness as much as possible.
Plus, in the same vain, gold is considered a measure of economic/currency confidence. They know gold will go up on a QE3 announcement, but they'd rather it didn't get too high. If they can engineer some volatility into the price of gold, they take away some of its credibility (maybe for fools who don't understand gold).