I still think the way to counter this is to associate something social ( "people-driven") similar to the Web of Trust with bad link databases (such as SURBL.org and URIBL.com) linked to URIs that are shared on FB. At least people could verify the honesty of the source, even if that is somehow fallible.
I used a similar scheme on a site that catches a huge amount of SPAM, Phishing and worms with virtually no impact on the system. It should not be so complicated for Facebook to implement it as well.
I made a post on Facebook that I think goes total in sync with your nice idea. Below inserted a translated version of what I wrote at https://www.facebook.com/lopolencastredealmeida/posts/10210500882618965