A rapid rise in price does not constitute a bubble. An artificial overvaluation that will lead to a sudden downward correction constitutes a bubble. The fluctuations in the price of Bitcoin are the result of the market's decision based on the choices of thousands of individual market participants. Emotionally, the reasons for price changes include: loss of confidence in Bitcoin, a large discrepancy between price and value that is not based on Bitcoin's economic fundamentals, increasing news coverage that stimulates speculative demand, fear of uncertainty, and outdated irrational exuberance and greed.
