Google announced a new targeting option for the Google Display Network named Custom Affinity Audiences.
Custom Affinity Audiences enables advertisers to create audiences that are more tailored to their brands, compared to Google's current broad, TV-like affinity audiences. Google offers an example, "rather than reaching Sports Fans, a running shoe company may want to reach Avid Marathon Runners instead. With custom affinity audiences, the shoe company can define this audience by:"
- using free form interests entered as keywords
- and/or using URLs as a proxy for interest bundles.
When creating these targets, Google, in real-time, will provide estimates for the people you may reach by showing breakdowns of their demographics like age and gender as well as their most relevant affinities.
Forum discussion at Google+ and WebmasterWorld.