Recently one of the larger and more well known Bitcoin exchanges, Mt Gox, ran into some difficulty. Basically the exchange stopped all transactions leading to a predictable drop in value as a significant part of the market suddenly became a whole lot less liquid and confidence in the cryptocurrency took a hit.
Of course this has lead to some of those who have Bitcoin with Mt Gox to call for the Japanese authorities to step in. Which is interesting, given one of the reasons that Bitcoin gained popularity; “Others who mistrust their national currency have seen Bitcoin as a safe haven from inflation and a way to circumvent capital control”.