Soros made his money because Bank of England was keeping the pound's value above where the market wanted it to be. (Soros being a large part of that market, but that's another issue.)

No government institution is going to be holding bitcoin's value anywhere. In a large, fully mature market, this wouldn't necessarily be a problem, because bitcoin would just trade at whatever its true value was. In a smaller market, especially an opaque one, it will be pretty easy to temporarily manipulate the price for fun and profit.

I'd be ready to chalk up this drop to a speculator, except I doubt the market is mature enough to support arrangements that would enable reliable short-selling. The run-up is definitely at least partially orchestrated, however, and not by the guys who write public blog posts titled "why I put all my savings in bitcoin."