Whether they originally set out to or not, when Zuckerberg and cohorts built Facebook, they also built perhaps the most powerful marketing platform/tool ever created (only Google gives it a potential run for its money).

Facebook is a place where users will actively, willingly offer up huge amounts of data about themselves. This includes demographic data such as their age, sex, and location – but also deeply personal information such as their hobbies and interests, where they went for dinner last night, and even their income bracket.