You might notice this in your Facebook feed:

It does work. Wanna know how?

Facebook lets you tag people in status updates, comments, etc. by writing @Joe Schmoe. (You can tag them without any special characters too, but this works quicker.)

Facebook also identifies people by user number. Apparently that number corresponds to how early that user signed up for Facebook. @[1:0] through @[3:0] are null, 4 is Mark Zuckerberg, 5 and 6 are his co-founders Chris Hughes and Dustin Muskovitz, 7 is his college roommate Arie Hasit…

So all you’re doing is pulling up the name of one of the first thousand Facebook users. If millions of people play the game with the rule above, they’ll all be naming the same thousand people.

Theoretically you could use more than three digits — there are over 845 million Facebook users, so once that tops a billion you have a full six digits to play with — but your full phone number won’t always work until there were 10 billion users, and we don’t even have that many people yet, like, anywhere.

I found this game through Tim Grinter via Tom Leveritt. Now you can spread it and how it works, and impress your friends.