First it was tulips. More recently it was tech stocks and then the housing market. Lately, its all about bitcoin.
All four share a common denominator: They suffered through financial bubbles, or bubble-like conditions. The first three ended badly. The jury is still out on whats in store for bitcoin.
Bitcoin could be in a bubble but no one knows for sure. This is cutting edge technology that is not even mainstream yet so it may just be breaking out into the mainstream investors.
We also have to consider the deflationary design of Bitcoin. Its not like a fiat currency that a government can print at will. Rather its a scarce commodity with a fixed limit to the supply that is harder to mine as time goes on. Basically its designed to be harder to get over time which should be making the price increase.