These videos are examples of bets you can make with your friends (or strangers) to scam them into buying you drinks at the bar. My advice would be to do it with your friends so you don't get your ass kicked. Also, you should probably practice these before you attempt to get a free drink out of someone in case you fail miserably and end up being the laughing stock of a party, and in that case your an idiot.
One thing I don't understand is how they can get so many free drinks and still be able to pull off all these scams so flawlessly...
Update: Most of these have been removed from YouTube and I'm too lazy to fix them. You can probably find most of them