Dot.com BS companies from the 90's that made nothing, but provided a service that nobody understood.

Hair salons that think they can charge like they are doctors, lawyers or any highly educated professions, ask me how I know, I'm done!
People who bought real estate, that couldn't really afford it, what I mean is no down payment! What did they really lose? Not their down payment.
Madoff Investors.
Anyone who bought Bank stocks, or any stock?