There is a story in Editor and Publisher magazine saying that "a newspaper reader in 2004 was worth $964 a year." While that has apparently slipped to only $500 per year (for several reasons, i.e.: teh interweb), Jeff Jarvis relates this line of thinking to the current, seemingly insane, $15 Billion valuation of social networking site Facebook, reasoning that each Facebook user is worth $300 per year. (I would imagine that this means advertising revenue, but I was too lazy to click through to read the entire article.)
$300 a year doesn't seem like that crazy of a number (less than $1 a day), so maybe that $15 Billion is not quite so insane.
How much revenue are you worth to Facebook? And if you don't facebook, why not?