But definitely, can't be considered as a financial pyramid by definition. You can invest anytime you what, and you don't need to market it by any sense. And its up to you how much money you going to put up. And no single person is benefiting if you are going to trade (buy/sell). The appropriate term should be "investment portfolio", in my opinion. Because the moment you buy, you hold that assets, which in this case bitcoin. And you have total control of it + privatekey in your wallet.