I think that since QE2, many people are trying to protect their wealth by selling dollars. Maybe that's why bitcoins have increased its price so much.
Panic selling the USD for BTC

i doubt it...IMO the current exchange rate is the result of speculation and hoarding, there's 5 million BTC out there yet only a fraction of that gets turned over at exchanges, just look at today's MtGox spread, High:0.97Low: 0.845 with that sort of volatility the exchange rate could go anywhere.
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I'm sure there's a reason why MtGox doesn't have USD accounts? i mean why the muck around with liberty reserve?