This is interesting, I was just thinking about this today.  Seems like a lot of people invest in crypto currencies along with traditional markets such as stock, bonds, and futures.  It only makes sense that when the market takes a pounding, all segments are hit.  Bitcoin is no exception to this rule.  The wise investor buys when everybody sells and sells when everybody buys.  At least, that's my best guess.  I'm going to stick with it because I love the technology.