Buys are coming in because Bitcoin will soon be in the faces of every Facebook user via ChangeTip. Lots of new Bitcoiners will soon enter the space due to this increased exposure.
Does changetip provides pay by PayPal or credit card
? Otherwise, don't think the Facebook user will bother open an exchange account or coinbase account just because they see some tips in BTC.
EDIT:
Just tried by myself. New users get $0.5 for free and then they have to either top up by BTC or have to register a coinbase account. Really wish them to provide a BTC purchasing service by themselves, otherwise I don't think that will attract many non-bitcoiners.
Yeap, I gave it try and it's easy, and there are lots of little businesses on facebook that could benefit... But customers actually going through the process to get bitcoin, and people cashing out from bitcoin need to be just as easy rather than a massive pain in the ass....