The individual who sells the Ponzi scheme makes money by siphoning off a large share of the money coming in. In other words, he does not make the investment. But Bitcoins are unique. The money was siphoned off from the beginning.
Only true if we see Satoshi spending his Bitcoins.
We have an online store selling baby products and really want to accept Bitcoins but we can't at the moment since Bitcoin is not widespread and price fluctuates madly. Once everybody got some and price is predictable in the short run, we'll show the finger to the bank, the real one siphoning from our pocket as commissions without actually providing any reasonable service.