but growth alone won't lead to a crash

True, but hubris does. The Smart money is going to Bitcoins, a bit (to coin a phrase) like it was going into vintage cars in 2006/7. The wide boys had done with property so looked for other things that had worth but not so much price, yet. Then the cars overheated and they moved on to something else, leaving the schmucks to realise there were hidden toxic debts and cars that were basically just er um cars with a bit of history. Rarity, of itself is meaningless, but desirability has a price, a value but little else unless someone else values it. And that is ephemeral.

Maybe the smart money has moved on from Bitcoins and it is the herd that desperately wants its value to be true. There are pundits prepared to publish at length on the volatility of Bitcoin (et al) and its variability. What can you buy with Bitcoin? A criminal's charter, for certain.

Bubbles are cyclic. Like bubbles they appear over there, not where they appeared last time. Some bigger than others. Predicting where and when is the smokescreen, and only for the lucky & the brave (who ain't gonna share their wisdom).

Let me see. In no particular sequence or timing: South Sea, Scotland's American Colonies, the Wall Street Crash, DotCom, Black Wednesday/early 1990s, 2008.

The cycles are about self-regulation if the feedback is in place or forced regulation when it is not. It is caused by inevitable latency of either. With herding actors in the system, and a lot of greed, it is an inevitable feature.

I don't offer solutions, or work-arounds. Just an observation, and I do predict deja vu.