What are some notable scams in history that went unnoticed for so long?

does it

Well, my transaction went through, so yes.

I agree that it is wasteful and overall a bad thing... now that I think about it could be somewhat excusable if they adopted a PoW algrothim that actually solves socially-useful expensive problems like protein-folding, through distributed computing.

But that doesn't make it a scam. There's not really any trickery. It's just bad.