Facebook quietly launched — or at least began testing — a new tool that has the potential of being quite useful for marketers: Audience Overlap.

Facebook ads cheaper and more effective than most other forms of advertising, including the popular Adwords.

Facebook is changing how it charges advertisers for click-based campaigns to make sure that, in return for their money, marketers are getting more than social currency.

Brands already incorporate social media photos from consumers into their next big advertising campaigns. Now, there's a new way for them to promote those images in Facebook campaigns too.