Bitcoin Craze is a Bubble, Just Not The Bubble You Might Think
The idea of monetary currency is a funny thing when you sit and think about it. A twenty dollar bill in your pocket only has twenty dollars worth of purchasing power because enough people have agreed that it does. Yet, there is nothing intrinsically valuable about the paper you hold and the number that is printed on it.
Enter the bitcoin. The controversial digital currency is (literally) of no value in the real world, unless enough people agree that it should be worth something. In that case, the value becomes real, and you can make actual purchases with it. And Bitcoin, like any currency, has its perceived valuation ebb and flow from time to time. This happens every time it hits the news for good or bad reasons.
http://fusion.net/modern_life/story/bitcoin-bubble-bubble-415227