I'm quite amazed where these huge sellers get their coins from.
Remember those 850.000 bitcoins "lost" on the MtGox? Somebody has the private keys of those BTC. Ask yourself what would you do if that was you. Would you hold all of them, or would you convert some to the fiat?
If Bitfinex equalised their fees so that the cost of borrowing a bitcoin approached the cost of borrowing USD we might see different price action.