Well bubble were caused by the huge whales who are buying a large amount of stocks or commodities.
Just look at the housing bubble. That was caused by millions of ordinary people buying houses that they ultimately could not afford.
A bubble is caused by speculative buying by many small investors. It may be triggered by whales making large buys, but it isn't a bubble until it becomes mainstream.
We are not there yet, but it will be time to exit when you see waves of newbies talking about how much their bitcoin investments are worth.
I would agree with this. True, whales may collude to pump up a commodity but it would take a number of small participants to really push it up. The initial boost makes it attractive to newer players.
This is actually making me nervous. I started around December last year, and just held on to my btc despite the mini-plunges. I waited long enough to trade, actually wouldn't have if I was not egged. "Oh come on, how will you get more btc without buying with your fiat?".
I did my first trade last night - I bought XRP.
Now I'm wondering if that is just money down the drain...