In early 2011 there was a site called Bitcoin2Cash. It offered to exchange Bitcoins for physical US Dollars delivered in the mail. The exchange rate was staggeringly low but at the time it was the only game in town for getting cash for Bitcoin.
For 1 Bitcoin you would get 0.006 cents.
And people sold to this guy! He raked in over 75,000 BTC (currently worth over 7.5 million USD) during the sites short time of operation.
I personally sold him 5000 BTC in what I consider to be my biggest Bitcoin blunder.