When there is a rapid growth in any of the crypto-currencies and assets such as Bitcoin, Ether, Zcash and others, many will call it out as a bubble. Indeed, on a relatively short time scale it clearly looks like a bubble.
The entire crypto-currency market capitalisation currently stands at around US$100 billion; it was US$60 billion one month ago. But Bitcoin was worth 1/100 of a US cent in June of 2009, 7 cents in June 2010, and US$7 in June of 2012.
Recently all eyes were on Ether. Over a 90 day period, Ether appreciated twice as quickly as Bitcoin did in late 2013, when Bitcoin crashed to around 35% of it's highest value. Aside from the 2013 crash, Bitcoin has experienced smaller crashes many times since, but is now worth double its 2013 high.
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