Well, if ever it were possible to definitively give reasons, this would be the time.

When you have, on the same day:

a) Greenspan's announcement saying bitcoin is a bubble, and using the "no intrinsic value" argument

b) China effectively banning bitcoin (not that we have the specifics to say that "ban" is the best term yet)

...it's not going to do wonders for the price.

Both (a) and (b) have been stated forever. (b) was just common knowledge, clarified with an official announcement today.

Yeah, but Bitcoin's price is not based purely on logic. It is also based on emotion.