"To make a nice soup: you need it to bubble for a while"
So the whole definition of bubble is being misinterpreted, for example Property was in a bubble = still there, still buying / selling. Internet companies were in bubble = internet giants are stronger than ever, after some weak projects collapsed stronger became more stronger. Next: banks were in bubble with their credit lending and credit swaps = look at them today, their balance sheets are stronger than ever. Their capital is larger than ever.
So is Bitcoin in a bubble? I think it is a cycle when some noise has to be removed, and then the real quality projects will thrive.
RE: What's the real cause of the decline in Bitcoin's price?