There's been a lot of speculation off late on the quality of Facebook fans, Facebook profiles & how they are affecting the Ad spend. Also, the crashing down of its stock price isn't helping their cause either.
Facebook just released this Infographic to show how effective their Ads are. Facebook reportedly has 995 million active users & about 67% growth year over year on the mobile front. They are also trying to push the Sponsored Stories Ads which are are already visible on the mobile & tablet versions along with the desktop version.
View the high resolution file here