In December 2011, the first bitcoin bubble ended when someone hacked Mt Gox and sold every bitcoin that was possible, clearing out the entire mtgox orderbook. How many bitcoins would you estimate were on Mtgox then? Maybe the hack mostly took place then and mtgox has been slowly covering for what happened ever since.

I think I remember someone on bitcoin talk at the time mentioning that their massive buy order for bitcoin at $0.01 went through.