On June 7th, 2012, the price of gold dropped by $22 in less than a second, guided by a computer algorithm during late trading. Sharp price drops in gold, for example $10 within a few minutes, can be observed frequently.
Interesting piece by Dimitri Speck.
Here's a snippet:
"... High frequency programs which now account for a significant share of trading activity have rightly fallen into disrepute in recent times. They might be useful in some cases such as avoiding market impact while placing large orders. However, unequal access to the market is questionable as are highly technical efforts which are ultimately done only to pull money out of the pockets of slower market participants. At the very latest, limits of legality are touched when high frequency programs are used for front running or to manipulate prices. Such a price manipulation took place on June 7, 2012, at 9:21 PM and 20 seconds in form of a high frequency attack on gold. One second was enough to manipulate the price of gold down by more than one per cent for the duration of several hours. ..."