...earlier commentary, I wrote that it seems to me that Facebook inflated its genuine user numbers (wildly underreported fakes) at its IPO, and that the problem is ongoing. Since writing my earlier commentary citing my unscientific survey: "Facebook's Fake Numbers: 'One Billion' Users May Be Less Than 500 Million" (Huffington Post - December 12, 2012), and after a Facebook spokesman responded to it (see update within the commentary in which the Facebook spokesman responds...but not to the numbers), I was amused to see that the Facebook "like" icon number in the upper right corner on Huffington Post dropped from 363 to 127. Perhaps Facebook is weeding out fake profiles and responding to my numbers after all. (Let's see, if I apply that ratio to "one billion" users, that would leave around 35% or 350 million genuine users. Well, it seems Facebook and I are in agreement!)
Facebook has a big problem with fakes, impostors, and double/triple/quadruple counting of multi-platform fakes and users. If Facebook wants to claim it has one billion genuine active users, then it must defend that seemingly wildly inflated figure. To me it appears to be mostly baloney.
My point is that as an advertiser, you cannot be assured that you are targeting real people, that the "likes" reported are real, and advertisers should independently verify that charges aren't from bot clicks. There's also no reason for you to take Facebook's assertions of advertising effectiveness as genuine. It seems to be very generous in claiming cause and effect for advertising revenues, but it's interesting to note that an experienced advertiser like GM doesn't spend on Facebook, but it spends advertising dollars on Twitter.