In case you were wondering just what the heck was going on, here's your explanation. For the first time, traders have levered access the Bitcoin market, and it's showing. In just seconds, the market jumped nearly 50% on huge volume.
It remains to be seen if things will settle out, but for the time being, the market remains quite volatile. Bitcoinica is suddenly the second biggest Bitcoin exchange, by volume, and it's been open for less than three days.
***UPDATE*** Bitcoinica now posts their trading volume on their home page - it's now up to 19,000 BTC over the last 24hrs. Incredible.