so yet again someone puts 2k+ coins on Stamp and Finex and pushes the price down on Huobi, who the hell can afford to sell 5k coins every few days for weeks? It's like he waits for the last batch to clear to the bank before selling another 5k+
Miners. They make 6 * 24h * 25BTC = 3600BTC/day. They have to sell them to cover the cost of electricity + equipment.
Yes. I think this is a factor with the development of huge asic farms.
BitFury are supposedly dumping what they mine. Their hash rate is up >60% in 1 month.

This, plus the bitcoin-accepting merchants which convert to fiat immediately (while old hoards are spent more than new ones built up), create the downward pressure at the present time.