What is the economic impact of Facebook?

Here is some media coverage of a recent Facebook study of its economic impact in terms of revenue and jobs.  Facebook claims it added $227 billion to the global economy, but they approached the question the wrong way.

The correct method is to treat jobs as a cost of Facebook, not a benefit, admittedly that is not how politics works nor is it how corporate PR works.  We should measure the benefits directly by consumer time use studies, much as Austan Goolsbee and Peter J. Klenow did in their paper on the internet (pdf).

My question today is this: what is the most accurate one line back-of-the-envelope estimate you can come up with for the gross benefits of Facebook, not bothering to subtract for the costs of running the site?  Here is one (hypothetical and illustrative) example, for America only:

100 million regular users, one hour a day, time valued at $10 an hour, and multiply for $365 billion a year.

You will notice this method implicitly captures the value and disvalue of the ads on Facebook.  The better and more useful the ads are, the more time people will spend on the site.

I don’t devote time to Facebook (I can thank MR for that), so surely you can do better than I in building a plausible one-line estimate.  Please leave your answer in the comments.