Update: see my post “Fixing Facebook with userContent.css” for a corrected and more extensive way to go about this. There are some stupid errors in this post that lead me to use a bad approach, but the greasemonkey script should still work.

I am not a huge fan of ads. I say that somewhat hypocritically as adSense proudly barfs somewhat random ads out on this page, none of which I really expect will ever click on, but that is besides the point ;). Anyway, I can normally block ads with adBlock, but social ads are trickier. Every social ad div has for a class:
feed_item clearfix social_ad
Each one is a seperate class. They do some trick so it is hard to override with a page wide css that doesn’t take out everything, so userContent.css and similar tricks are out. I ended up brute forcing it and writing a greasemonkey that does the job.

Download it here: hidefacebookfeedadsuser.js

Update: There is another class used as well. If I remember correctly, instead of social_ads, its ad_capsule with everything else the same.