There are things that are even worse. They are the naive and unsophisticated business plans. Look at TSLA, Uber, TWTR, SNAP etc. They are just disasters. People would still invest in these and they won't immediately give gigantic red flags like scams. A bad business can do more damage than a ponzi. Lots of good people who haven't done enough research could get burnt by these. One good example is Aeron. I don't think it's a scam. I'm 99.99999% sure it's not made to be a scam. But I'm 100% sure that it's a disaster investment.
https://steemit.com/blockchain/@vimukthi/aeron-arn-whitepaper-reddit-analysis-along-with-opinions-from-aviation-veterans-and-how-smts-can-create-something-better
https://steemit.com/blockchain/@vimukthi/aeron-arn-review-in-depth-analysis-investing-after-the-safest-year-in-aviation-in-history