Someone saw silver take a quick dive and wanted to move out of bitcoin and into metal?:
https://bitcointalksearch.org/topic/btc-dump-and-silver-smackdown-at-the-same-moment-127897
https://bitcointalksearch.org/topic/btc-dump-and-silver-smackdown-at-the-same-moment-127897
Interestingly sounds like the silver drop was a glitch on kitco's part.
https://bitcointalksearch.org/topic/m.1359722
https://www.kitcomm.com/showthread.php?s=3815d15b62ab15a50e63e41d8a7d5ded&t=111547
I can't think of a way to move money from Gox to a brokerage fast enough to do that.
As wrend speculated in the other thread:
it is possible that we have a hedging bot working on auto, and some biggish (5000BTC) individuals that closely follow Silver?
You do not need to use the same money you get from selling BTC to buy silver, you just need money available.
Buy PM with available capital and close position in BTC simultaneously. A bot could see the kitco drop and execute an order for PM and a sell for BTC right quick.