As Facebook has grown from a collegiate social network to a site that gets action from 7.3% of the world’s population, it has also evolved into a marketing tool. One report estimated that advertisers will spend $4 billion on Facebook advertising this year. Facebook didn’t come out of the gate as a marketing-friendly product in 2004, and it has conducted a fair share of failed experiments in its efforts to become one. We’ve chronicled its evolution in the infographic below. -- sarah kessler