Facebook officially filed its IPO on Wednesday. The initial public offering is expected sometime in May and will value Facebook at $75 billion to $100 billion. The company generated $3.7 billion in 2011 revenue. As strong as this figure sounds at first, a savvy investor should look further in to its financials to see how Facebook generates so much revenue. It is reported that the social media titan generated 85 percent of overall revenue from advertising.  Read more