Facebook describes the offering as a "new way to target ads to more categories of people." Partner Categories builds on Custom Audiences, a program it launched in September and then augmented in February using third-party shopping data from firms like Datalogix, Acxiom and Epsilon. That February expansion let advertisers target by broad categories, including people who are in the market for a car.
Now, advertisers can target to 500 specific segments, including "Dairy and Egg Buyers" and customers looking for a full-size sedan rather than just any car. A Facebook rep says that if a category is too large (i.e., expensive), you can narrow that down by cross-matching with other categories. For instance, you can target fewer users by searching "Children's Cereal Buyers" with "Arrested Development fans." But you can't just say you only want to target X amount of Children's Cereal Buyers.Facebook Expands Ads With Partner Categories [mashable.com]