In a fraudulent investment scheme, like Ponzi, investors transfer their utilizable resources, be it money, goods or services, and then they end up to with something which has zero utilization capacity, like promise or non-binding record of investment. After the investment, the only possible way for them to get utilizable resources back is if new investors join the scheme and in that way bring such resources with them.

The opposite is true in a legitimate investment business, where investors transfer one type of utilizable resource and in return they receive another type of such resource. An utilizable resource is anything that can be practically utilized by humans. For e.g. a car can be practically utilized for driving, a dollar for loan payments, a stock for participation in company's profitability, food for providing nutritional support, a raw material for producing finished products etc. Hence, an utilizable resource is not something that is just passed from hand-to-hand on a market for investing or speculation purposes, but something which has final users who will consume, utilize or otherwise put the thing to practical use. And this practical use by final users is how things got to the market in the first place. For e.g. dollars got to the market because they have final users the same as food. In other words, loan contracts and collaterals force people to use dollars for loan payments the same as hunger forces people to use food. Since all dollars (either paper or digital) are loan based, they are not just passed from hand to hand, but also utilized by borrowers who are forced to give goods and services to dollar investors, speculators, or regular users, when loan payment liability must be fulfilled. In the same way hungry people are forced to give money goods or services to food producers.

In a fraudulent investment scheme there are no final users, which is why a thing that lures members into the scheme is just passed from hand-to-hand, from member-to-member... until it is realized that the only profit can come from utilizable resources invested into the scheme.

And 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. And this number cannot be practically utilized like food is utilized by hungry people or dollar by borrowers, but it can only be passed from address-to-address, from hand-to-hand,  from member-to-member. And this is exactly how classical fraudulent schemes operate - they use something to lure people into the scheme, but the thing itself is non-utilizable, which is why it is just passed from one person to another. Once people realize that profit or utilizable resources can come from new investors only, the whole scheme collapses. And this is the ultimate fate of bitcoin. So, do not buy it.