Like Google AdWords quality score shows a 1 to 10 score to advertisers, now Facebook is doing that for their ads.
Facebook announced they are showing "relevancy scores" on an ad by ad basis to advertisers. The relevancy score is based on the "positive and negative feedback expected an ad to receive from its target audience."
By positive or negative feedback they mean views, conversions, clicks, comments, likes, etc etc.
Here is a picture of what the score may look like:
Facebook added:
Ads receive a relevance score between 1 and 10, with 10 being the highest. The score is updated as people interact and provide feedback on the ad. Ads with guaranteed delivery - like those bought through reach and frequency - are not impacted by relevance score. Relevance score has a smaller impact on cost and delivery in brand awareness campaigns, since those ads are optimized for reaching people, rather than driving a specific action like installs.
Forum discussion at WebmasterWorld.