Millions of ads are bought on FBX every second via demand-side platforms that plug advertisers into FBX. Billions of impressions are served every day. Facebook accounts for about half of retargeted ad clicks.
Real-time bidding is key as it's impossible to target a user who is interested in living room furniture with personalized ads when they open their Facebook page unless he or she can be identified and served a relevant ad in milliseconds.
FBX assists "demand fulfillment" by nudging shoppers to complete a purchase they've already shown interest in.
FBX produces comparatively good results considering cost and performance. FBX platform continually learns and improves. See improving News Feed placements.
FBX is not yet available on mobile and Sponsored Story social-native ads (heart of Facebook's ad ecosystem) aren't accessible via FBX. FBX News Feed ads are still limited in terms of their social features.
See Report: http://bit.ly/1cDQ5XC