Bitcoin falls perfectly under the general description of an pyramid scheme. Wikipedia: "A pyramid scheme is an unsustainable business model that involves promising participants payment or services, primarily for enrolling other people into the scheme, rather than supplying any real investment or sale of products or services to the public.". Only thing different from the pyramid schemes that we see everyday is the general reward system where the entire pyramid is rewarded for new recruits.
This is beginning to look like another repetitive "semantic game." What you call a "pyramid scheme" others would define as building up a P2P-proof-of-work-trusted-Network, which becomes stronger and of more value with each participant. Where you interpret a relation between diminishing amount of participants and value, others understand that the rise and fall in price follow directly upon good-or-bad news about a future digital, yet vulnerable, currency; any new currency has to deal with volatility in the beginning. Nobody can know for sure wether this Bitcoin-Network is sustainable or not, whereas you seem to have some fortune-telling capacity predicting the latter. Anyway, my common sense tells me you are deliberately trying to spread fraudulent information.