There's a game out there where all you do is invite other people to the game. Thats it. You have 30 days to invite someone, and every time you invite someone your timer resets to 30 days. If it reaches 0, you lose the game.
Each person you invite earns you 32 points, each person invited by somebody you invited earns you 16 points, etc.
Here's my link: http://en.wikipedia.org/wiki/Pyramid_scheme. I know referral links aren't usually allowed, but for this particular game you need one in order to play, so I figured you might as well use mine?