I'd love to get an economist studying why the value of bitcoins goes up. After all, they're infinitely reusable, totally fungible, and incredibly low friction. The only reason for their value to rise (rather than them just being passed around at the same price indefinitely) is if people expect them to rise, or if there's a shortage (forcing people to use fractions of a bitcoin to represent the same number of dollars…
So the question is how are the marginal supply and demand determined? The marginal demand is subject to spikes in interest, media coverage, the Cyprus crisis (I really doubt the latter is meaningful but perhaps it makes people everywhere think they want to move out of bank deposits. People certainly attribute things to it). The marginal supply is based on (1) mining, which happens at a fixed rate and (2) people who wish to exit Bitcoin, which is subject to lots of whims.
Lots of evidence shows that most Bitcoins are hoarded, so it's possible that what we see is just a supply crunch - nobody wants to sell their Bitcoins and some people want to buy. I suppose the natural way to answer that is to go look at historical exchange volume across all the exchanges (or, as a first-cut proxy, just Mt. Gox).