I was wondering, do people realize just how crazy and obvious the first Bitcoin bubble was?... In a matter of just 8 days we went from 8.741 to 29.6, which means the closing price more than tripled in just over a week...
What do you think using the first bubble as a baseline for this kind of thought?
Like all bubbles, it's easy to see with hindsight.
But before the first bubble, there were many times when the price more than doubled within 8 days. For example, the MtGox closing price went from $1.41 on 22 April 2011 to $3.50 on 30 April 2011, but that wasn't a bubble. It went from $3.33 on 5 May 2011 to $8.20 on 13 May 2011, but that was not a bubble. It went from $0.45 on 28 Jan 2011 to $0.92 on 5 Feb 2011, but that was not a bubble. (There are more examples).
I think you are right that the price tripled within 8 days only once. But at the time, how sure could anyone be that a tripling would be unsustainable when all the doublings had been sustainable?
Long term, you can say that more than 7% per week is unsustainable, but I don't think you can say anything about the short term, without the benefit of hindsight.