My favorite:

I knew a guy who had a company that was going to do something arguably interesting in the field of communications. So he raised money, hired a couple of guys, and bought space announcing the product on a huge billboard in San Francisco. There was no product, this was purely aspiration, but that was the kind of thing people did at the time.

And of course, an even bigger company with a huge valuation immediately bought his company for over $100 million, payable in their stock.They did almost no due diligence, but apparently thought very highly of that billboard.

So he goes to work at this other company, because part of the deal is he has to be there three years for his shares to fully vest. On about the third day he's told, "We like you, you're a good guy, but we don't feel we really have a position in senior management for you here. You can go - here, you're fully vested."

This guy is a very smart operator, and before he gets to the parking lot he's thinking "Wait a minute - they bought a company without knowing there was no product, and they just let go of the guy who knew there was no product, and who knew how to fix that and make the product. These people are clueless - I'm shorting the stock." So he cashes his shares and buys a lot of put options, as far out as he can get them.

Fast forward a couple of years - the bubble has popped, the guy has moved on, he's basically forgotten about the put options he bought. His broker calls.

"Hey, what do you want me to do with these puts?" the broker says, "they're about to expire." Guy had moved on to his next company, and hadn't noticed that the stock he'd shorted at $200 was now worth $2.50 a share. He cashes the options, for a net personal take of $200 million.

Not bad, for renting a billboard.