The sell off was one very very large sell order. The ticker did not update until the order was finished processing. I watched it get processed in real time on
http://bitcoin.clarkmoody.com/time-sales/The messages you got in between ticker updates were the many buy orders getting filled one by one.
I thought about this but...
If this is the case, how did that one guy produce a youtube video watching the price fall with commentary? -or- rather, if i understand the purpose of clarkmoody: how does clarkmoody get 'real time' information about the sale in progress when the websockets stream does not push it?