Concurrency should not be involved in scam
I have seen several cryptocurrencies go into a scam after their project didn't go successful that their admin wants it to be or they just disappear whenever they got enough money from investments. Some happen during Initial Coin Offer or force their members to upgrade in order to receive benefits from sites.
I have read in an article about OneCoin that is involved in a very large scale pyramiding scam. It was really bad that many people lost money from their hard-earned. The bad thing about this one that even the authorities that are involved in resolving the case and confiscated the money. People who invested it will surely lose it and never refund it back to members as it is considered as a fraudulent scam.
I am sure that many people who don't really understand what is a cryptocurrency invested as one of their family members or even their trusted friend recruited them without even explaining the details. On the other hand, the investor will probably think that the money that has been invested in the platform will grow longterm but what happens it disappears.
I am hoping that cryptocurrency owners should be honest, the same with many other cryptocurrencies as we all know that cryptocurrencies grow as long as they fully developed it. So I think there is no need to scam as they can always earn on their side too.