https://phys.org/news/2018-06-criminals-cryptocurrency.html

But that is only true if transactions happen within the system. And there are other elements of cryptocurrency technologies that actually make fraud easier.

Some of the problems the Justice Department is investigating appear to have arisen because bitcoin enthusiasts are not treating cryptocurrencies as a means of payment like dollars. Rather, they're behaving as if bitcoins and their ilk are speculative assets like stocks and bonds. So they're placing orders to buy bitcoin in advance, only later completing the deal. One type of fraud investigators are looking into is called "spoofing," in which people place orders but cancel them before the deal is finalized – often without even having to pay a service fee. That makes it look like there's more demand for bitcoin than there actually is, driving up the value of each bitcoin.