Wouldn't there be some supreme value to being able to use Facebook as a retargeting tool for your business?
I think Facebook's appeal for businesses is essentially that it's not home to traditional marketing messages. Relationships with consumers can be fostered on Facebook (through your business page) in a non-threatening / non-hostile environment.
So what if we could identify consumers on Facebook that had been on our website within the last say 60 days and retarget them? I just happen to think Social Retargeting (when possible) would be a hell of a lot more welcome and efficient than say a lot of general retargeting on the web.
Does the technology exist to make this happen? I imagine Facebook (for some good reason) would make this very difficult to execute.