Clarence - 3:15 am on Aug 4, 2012 (gmt 0)
Fake accounts don't affect Advertiser Impressions or clicks, so it's not a big deal to Facebook's Bottom line.
Advertising pays for Facebook. Actual logged in people viewing impressions, and actual people clicking on ads.
Don't confuse Facebook's press with Facebook's numbers, and Facebook Advertiser base is increasing Exponentially "Faster then Google".