This finally brings us to bitcoin and the following question. When investors transfer their utilizable resources like money, goods or services into bitcoin do they end up with another utilizable resource, i.e. a resource which can be utilized by some final user? Well, the obvious answer is: no, they do not. Instead, they end up only with a record in a table(blockchain) or in other words, only with a number associated with their bitcoin address. Since this number cannot be practically utilized like food or dollar, that means that investors engaged in a one-way transaction. Now the second question. Once investors engaged in such transaction, how can they retrieve utilizable type of resources back? Well, you guessed it right. The same as in a classical Ponzi scheme or any other fraudulent investment business - new investors must step in and engage in a one-way transaction like they did.
Therefore, bitcoin is neither money nor asset nor payments system. Money and assets are utilizable resources, while payment system is means to transfer such resources from one party to another. Bitcoin on the other hand is a mere record of the fact that investors handed out their utilizable resources for free, just like in a classical Ponzi scheme.
Umm...what? You do not just get a record, you actually get
spendable coins, which is a utilizable resource on its own.
Everything is a series of one-way transactions, even traditional cash payments (you give them money, they give you what you pay for), so why are transactions in Bitcoin any different?
The way you're trying to tie it up neatly to a bow as a ponzi is a reach, too. Ponzis lure investors, and use the new investors' money to pay out old investors. Bitcoin has no payouts whatsoever -- it utilizes the simple concept of supply and demand to gain value. It has nothing to do with handing out utilizable recources, for free or otherwise.