thanks
Several reasons for the drop:
1. Panic induced by a whale selling since the beginning of September. (regular dumps of ~1000BTC between 5 and 8 UTC on bitstamp).
2. The innitial sales broke below $340 which was the old bottom and caused even more people to bail out.
3. There was a bearish trend since the double top at $660 (stamp price) in July, which only maade things easier for the dumpers.
4. Some sad whale tried to manipulate the price by moving a $30k sell wall on stamp. Just a few hours ago the wall was eaten and we came back up over $300, which is bullish.