According to Facebook's February 1, 2012 regulatory filing, Facebook generated $3.15 billion in ad revenue in 2011. If you care to read this filing, search for the phrase "advertising revenue" and you'll get a sense of how dependent Facebook intends to be on this revenue in order to succeed. An April 2012 MediaPost article cited Pivotal Research Analyst Brian Wieser as predicting Facebook's 2012 ad revenue would grow "32 percent this year to $4.2 billion and hit $12.6 billion by 2017." So in May, when General Motors pulled its $10 million Facebook ad campaign right before Facebook's IPO, it rocked the ad industry probably as much as it rocked Facebook. But a new Q2 2012 report from TBG Digital, a leading Facebook advertising buyer,…