They are buying xrp.
This is the best theory so far, however it only accounts for a fraction of the volume in the past 24 hrs. There is an amazing inverse correlation between XRP and BTC happening:
https://www.ripplecharts.com/#/I think this is a miniature "perfect-storm" of events (note: not major). What I think is driving the price down is a combination of:
1. fears of regulatory clampdown in the U.S. and elsewhere
2. the exponentially-growing hashrate is finally collapsing
3. difficulty remains at all-time highs while mining revenue remains sluggish, with price
4. BTC is still up over 5-fold in 1 year and 54-fold in 2 years! Those are some darn fine returns to cash out on.
These charts do a lot of the explaining:
https://blockchain.info/chartsNow for the good:
1. Bitcoin can't be 100% regulated. It just can't.
2. Millions of dollars are currently being poured into bitcoin startup ventures and some of the resulting projects will be profitable. With many brains and dollars at work its hard to imagine they will all fail.
3. The supply curve... will begin to even out over the next couple years, meaning bitcoin will finally become deflationary.
I think mass adoption is key and will ultimately drive the price of bitcoin, not speculation.