Which begs the question, "Why is it stable?"  My bet is some big player is stabilizing it.  So is this person buying or selling?

Selling:
Loads of people discovered Bitcoins recently and want to buy some.  An early adopter with a lot of coins has a vested interest in making Bitcoins a success, so he is selling coins like crazy to keep speculators from creating a bubble (that means you grimex).  Bank of Satoshi Nakamoto perhaps?  This is a good thing.  Hopefully, other speculators will leave and things can stabilize again on their own.

Buying:
Loads of people are dumping Bitcoins and this guy is buying them up.  This seems unlikely.  Why would someone do this at $20?