Burger King recently introduced a Facebook app called Whopper Sacrifice that allows users to delete ten of their friends in exchange for a Whopper sandwich. Watch the app in action.

What BK has unwittingly done here is provide a way to determine the valuation of Facebook. Let’s assume that the majority of Facebook’s value comes from the connections between their users. From Facebook’s statistics page, we learn that the site has 150 million users and the average user has 100 friends. Each friendship is requires the assent of both friends so really each user can, on average, only end half of their friendships. The price of a Whopper is approximately $2.40. That means that each user’s friendships is worth around 5 Whoppers, or $12. Do the math and:

$12/user X 150M users = $1.8 billion valuation for Facebook

That’s considerably less than the $15 billion valuation assigned to Facebook when Microsoft invested in the company in October 2007 and the lower valuations being tossed about in recent months.

P.S. Other assumptions for the sake of argument: every user is eligible for the Whopper promotion (it’s actually only valid in the US), you can sell all of your friends for multiple burgers (actually limit one per customer), and the “average user has 100 friends” means that Facebook users average 100 friends apiece (no idea what the reality is…if they’re using the median instead of the mean then that number could be higher or lower). Oh, and it’s also assumed that no one should take this too seriously.

Update: I’m getting some email saying that Facebook friendships require the assent of both parties. Is that the way it works for the BK thing? If I am friends with Mary and I unfriend her through the Whopper Sacrifice app, is she then unable to unfriend me to help get her burger? If so, then the $3.6 billion valuation drops to $1.8 billion because each unfriending event takes care of 2 friend connections, not just one. Anyone? Note: we are already taking this too seriously!

Update: Ok, it looks like unfriending on Facebook takes out two friendship connections, not just one. So that drops each user’s share to $12 and the valuation to $1.8 billion. D. Final answer, Regis. (thx, everyone)