"don't allow likes from someone with more than 5+ likes in their account""
The # of likes by the user is a good proxy for how diluted the quality of the "like" is.
Probability_to_show_ad = constant * num_other_likes
That said, as long as Facebook has a counter-incentive to cleaning it up, we shouldn't expect this change. We need advertisers to revolt in large #'s before the financial incentives make this a priority for FB.
So I could buy 10 "Fractional Likes" and get 20 users who each only have 2 total Likes (including this one) = 20 * 1/2 = 10
OR I get 10,000 users who each have 1,000 Likes each = 10K * 1/1000 = 10
...which seems a reasonable ballpark for resolving it in an automatable, economic way.
"Don't allow Likes over X" kind of sucks since what happens to legitimate Likers? I'm not a clickfarmer, but I've Liked way more than 5 things.
My News Feed has turned to crap (probably because of it), but that's a whole 'nother story.
Either solution would require Facebook to admit that there are tons of fake likes though. The assumption being that admitting this will have a negative impact on revenue.
Also, either solution would probably result in a lot of new click far accounts being created with the new goal of keeping likes to a minimum. It'll be a constant battle I'm sure.