Last week, the massive social network announced that brands, advertisers, and marketers that want to run contests or sweepstakes on its platform have to go through an approval process first. Getting that approval could be a new revenue stream for Facebook: according to multiple sources in the marketing industry, they're being told that running a promotion in a Facebook application or "fan page" requires buying ad space too. It's pricey. The minimum ad buy is $10,000 for 30 days, using Facebook's self-service advertising system, according to documents seen by CNET, or $30,000 for 30 days of Facebook home page ads. Priority in the approval process will be scaled, based on how much advertising space has been purchased. - polou/indigo_bow from Bookmarklet