This is a valid concern, and the reason of existence and activity of OTC market for bitcoin is very real. However, any instrument that has an audacity to be traded in an open market must be able to handle this. This is free market. A free market can be manipulated, will be manipulated, and perhaps should be manipulated.

GBP did fall at that particular juncture, but it was just a trade. Many people, perhaps countries impacted by it. But it is still a trade. GBP still is around and traded. If BTC can't handle this, then perhaps it shouldn't be traded. In other words, what I am trying to say, if you want mass adaption, then you must be able to handle short sellers, delta hedgers, risk arbitrage maker..... all these. Because these things happen on a min by min basis in any fiat currency market. If we want to be big boy or girl, we got to come out of diaper :)

Bottom line deal with it. Because, much worse than Soros is coming our way :)