A few months ago in September, I attended the SES Conference in San Francisco. Here's a video interview I did with Brad Flora, CEO of Perfect Audience a Facebook and Web retargeting platform.
We talked about Newsfeed Retargeting which at the time was the newest addition to Facebook's retargeting capabilities. Recently FB announced their own native retargeting via Custom Audiences.
This is supposed to be complementary to FBX, and although it's not yet generally available to all advertisers, I expect it will be something that will compete for marketing dollars from FBX partners especially since it also allows advertisers to use all of Facebook's targeting capabilities such as age, location, interests and likes.