This runup is clearly being driven by buying activity from China. BTC China is now the biggest exchange. Bitcoins provide a legal (more or less) way to convert yuan to dollars or euros. (This normally requires permission from the State Administration for Foreign Exchange.)
But why is the runup so fast? Possibly because there aren't enough dollars flowing into the Bitcoin exchanges to satisfy the demand from sellers in China. People in China who want to convert yuan to dollars or euros don't intend to stay in Bitcoins for long. But they don't care what the Bitcoin exchange rate is, only what the yuan-Bitcoin-dollar exchange rate is for the brief period they're in Bitcoins.
Hm.
What is the difference between the dollar/yuan and dollar/bitcoin/yuan exchange rates?