I work at a cryptocurrency decentralized exchange that has recently converted into a DAO (Decentralized autonomous organization). I'm coming up on 4 years, with the last few months at the DAO.

The first thing that you need to do to answer your question is define "scam". The dictionary definition is "a fraudulent or deceptive act or operation", fraudulent meaning "having a tendency or disposition to deceive or give false impressions".

So the question is "was cryptocurrency invented under false pretenses or with the intent to deceive?"

The Bitcoin whitepaper is considered by most as the beginning of cryptocurrency. If one reads that whitepaper, I don't see anything there that could be to be deceitful or show intention to defraud.

The Bitcoin whitepaper proposed a system to allow individuals to hold and transfer a store of wealth between individuals without interference or control from third-parties (such as governments).

Bitcoin is an experiment. The author(s) identified a problem and created a solution, albeit an imperfect one. Since then, others have seen those problems and attempted to fix them. After Bitcoin we saw various forks of the Bitcoin code base to make coins like Namecoin and Litecoin. These were fundamentally Bitcoin with some minor adjustments.

We later got Ethereum which saw even more potential by using distributed consensus to create a world-wide virtual machine where people could run code to modify state. Smart contracts showed potential to do much more with digital currency than just send and receive. Contracts could be written and enforced by consensus without the ability of a third-party to intervene.

Continuing on, we saw more and more innovation in the space. One cryptocurrency uses a DAG to confirm transactions rather than blocks, which allows for much faster confirmations and higher transaction rates. Another protocol was created to allow inter-blockchain transfers (COSMOS,POKADOT) without an intermediary.

All of these cryptocurrencies are experiments. It's a massive engineering effort trying to solve a variety of problems, mostly around wealth management, but there are many others.

Now, to the point of fraud and scams. There are a lot of bad people out there that have no issue stealing from other people. Crypto is a relatively new technology and is designed to be free from government regulation. Because of that, it's quite easy for people to use hype and propaganda to exploit others.

There is nothing, in my opinion, inherent in cryptocurrency that makes it fraudulent.

For those that work in, use, or "invest" in crypto, this is all a long experiment that will likely go on for decades or longer. I believe that this experiment has, and will continue to, bring value.

edit: Cryptocurrency, specifically Ethereum and smart contracts, has allowed my company to convert to a DAO. A DAO is a fascinating way to organize and government a business. There is no leadership hierarchy. Governance is democratic. Everything is done publicly and in the open, including budgets. As an engineering group, we are no longer beholden to one individual's will. Everyone in the DAO has to come together to build toward a common goal. Not having a CEO (or C-suite of any kind) is incredibly liberating and we are building a higher quality product than we did when we had centralized leadership.