Facebook is a social network that has had the success of breaking into the social networking scene and surpassing its competitors all the way to its current position at the top of the social media sphere providing its services to over 400 million users.
Facebook provides a PPC (Pay per Click) service that focuses on the various niche markets that engage on the social network. The social site allows you to target your ads to only be viewable on specific profile pages.
Here is a view of the setup and the various demographics on Facebook:
