I figured that pirate had a lot of coins.. But, I had no idea that he had control of so many that it would make the market react this much... Or at least the perception. If/when Pirate starts paying people, I hope that they re-invest into things like GLBSE and other bitcoin related ventures.
Shallow pool means big players make big waves.
Rumour has it he controls approx 4% of total pool of available bit-coins, shifting even 2% would make some significant waves...