[tomkarlo]

I'm not sure that's comparable; that's rewarding ads for being more relevant to the original search (or penalizing ads for being less relevant.) CPC services get paid for clicks but have views for inventory, so it makes sense they'd favor showing an add where the chance of a click is higher, raising the CPM.

On FB, you're getting charged just to show the post, so it's more of a CPM model.