It seems that marketers can't get enough of Facebook.  During a period in which many companies were just trying not to lay off workers and/or go bankrupt, Facebook managed to increase the number of organizations advertising with it by over 400 percent.

This statistic doesn't come from a random blogger's back-of-the-envelope calculations or some data firm's small case study.  Brian Womack reported today, "Facebook . . . said its advertisers have more than quadrupled since the start of 2009 as marketers aim to get their products before a growing global audience."

Facebook didn't achieve that growth by hiring a crazy number of new salespeople, either.  Womack wrote that it just "doubled the number of salespeople last year from 2008, according to an e-mailed statement."

Either Facebook's salespeople are sprouting extra arms, then, or more than a few advertisers are approaching the social network on their own at this point.  Potentially many more than a few, too, since Facebook is notorious for being conservative when making information public.

Unfortunately, though, Facebook didn't share any more info (conservative or not) when it came to the very interesting subject of what sort of revenue all this advertising is generating.