37btc volume on bittrex today.
Muchos selling.
Some dumped at 20k but that was always going to happen when people can exit with 70% gains.
There was also a big arbitrage opportunity that lasted for a few hours, I'm not surprised to see this much selling on Bittrex.
Last night you could've buy at 20K on cryptsy/mintpal and sell at 22-23K on bittrex. The spread was there for quite a time.
So people were selling on Bittrex and the selling pressure is making the price drop a little more on higher volumes.
That's my theory at least.