neo9436 is dead on, too much supply.
For the most part the miners are having to sell everything they mine to pay for expenses, hopefully this shakes out the mass of miners as the price is too low to turn a profit for most.
Personally if I was going to be a miner, I would of had the capital to mine and hlod for 5-10 years, selling some along the high points but hoarding for the long term and retiring early.