I got this off Tim Hartford’s Twitter feed and he describes it as Prisoners’ Dilemma. I’m not so sure:
First of all, you are not allowed to give any online hints that you are playing. If you do, you cause unending shame to be heaped upon yourself. This defeats the entire purpose.
On each turn, you give your phone (which must have a Twitter client, signed in to your main Twitter account) to another player. For the first turn, you pass your phone to the person at your left, and in exchange you receive a phone from the person to your right. On the second turn, your phone is given the the person two people to your left, etc. When you’ve passed your phone to everyone around the table, the round is over.
When you receive a phone from someone else, it should have the phone’s Twitter client active, with whatever UI there is to make a new tweet. Then you enter in anything you want. Anything. There are no rules to this part. However, and this is very important: DO NOT POST yet. You may get to do that later. Instead, hand the phone back to the owner.
When you receive your phone back, look at the proposed tweet. Then hand it back to the same person who composed it.
If you don’t want them to post it, conceal a $20 bill in your hand. If you want to allow them to post it, put nothing in your hand. Making sure to hide anything that may be in your hand, put it forward onto the table. Wait until everyone has put their hand in, and then all of you must open your hands simultaneously.
If everyone has $20 in their hands, the money goes into the pot for the next round and nothing is posted.
If nobody has $20 in their hands, nothing gets posted.
If some people have $20 and some people are empty-handed, posts happen for those people who didn’t pay up, and the money (including anything already in the pot) is distributed evenly to those people who didn’t pay.
Finally, any tweets made during this game may not be erased at least until the NEXT occasion that the person plays the game.
I guess if you want people to suffer embarassment then no-one giving $20 is not an equilibrium.