Wouldn't bitcoin be a bubble (though maybe a pop-proof bubble) not a pyramid scheme? Because I thought bubbles are essentially decentralized pyramid schemes.

Hmm, I wonder what a decentralized ponzi scheme would look like.  Bitcoin except where there are higher transaction fees (to encourage people to hold on to money and to pay for miners) and for new currency to be created by people that hold onto their currency for long periods of time, rather than the miners?