There's a con game you can witness being played in San Francisco on many warm afternoons, usually between Pier 33 and Pier 39, a location designed to catch the tourists coming off the Alcatraz tour boats at Pier 33. It's called the shell game.[1]

The aim of the "game" is to bet money on which shell the ball is under after the shells are mixed up. It's played in many other parts of the world, and though in the old days was played with walnut shells, these days they usually use plastic bottle caps, match boxes, or metal cups. Instead of the traditional ball, these days they usually use a piece of chewing gum or wad of aluminum foil. Here's a video of a famous shell game hustler plying his trade: [2], and another of the shell game being played in Stockholm: [3] Many more here: [4]. The three card monte[5] is essentially the same scam, with three face down cards instead of shells.

The sad thing is that many people think this is a game of skill. But it's not. It's a con that's been refined over hundreds of years to non-violently rob you of your money.

Something else most people don't realize is that when there's a shell game going on, the shell game operator (the guy who mixes up the shells) is not alone. He's almost always part of a gang of between 4 to 8 people, each playing a specific role in the scam. Some of the most important pretend to be players, making noise, having a great time, and apparently winning lots of money, since the hardest thing to do in a shell game con is to get people to stop and play, and this is the main way they do it. They also have lookouts, who warn the gang if they spot the police, and others with various functions like smoothing over ruffled feathers of the losers or handling trouble. In the above videos you'll also see gang members regularly stand in front of cameras to try to block the view.

Unless the shell game operator is incompetent or wants to give the impression that the game is being played fairly (usually when no actual money is at stake), the mark will never be able to guess where the ball is, as the operator has a cheating move to make the ball disappear from under any shell and appear anywhere else he wants.. and if the mark ever does guess correctly, there are numerous ways the hustlers have of making sure the mark never collects his money. One common way is for one of the gang members to yell "police" and have everyone run away (usually with the mark's money). Another is for one of the gang members to "accidentally" knock the table over before the shell is lifted. If all else fails for them, they will often not be above just simply mugging their mark a couple of blocks away from the game.

Really, the only way to "win" at this "game" is to have a bigger gang.

Unfortunately, the police don't seem to do anything about this, even though they're usually well aware that the games are being played. I've been told by SF police that they know the shell game is going on there, but there's nothing they can do because as soon as they approach the hustlers run away. All they can do is cite them for littering, because they usually knock their cardboard table over on the sidewalk before they run away. I'm not sure why the police haven't just dressed as tourists, though. It should be pretty easy to catch the hustlers then.

[1] - https://en.wikipedia.org/wiki/Shell_game

[2] - https://www.youtube.com/watch?v=xRFlJVTT8FY

[3] - https://www.youtube.com/watch?v=AboNGr7RxKE

[4] - http://www.youtube.com/view_play_list?p=61150A4524304AB8

[5] - https://en.wikipedia.org/wiki/Three_card_monte