Facebook now has an option to hide individual posts? Does this train Facebook as to which posts are interesting?
I do not believe it does. In the faqs, facebook makes no mention of "Hide this post" influencing what gets displayed, but they do say that "Mark as Spam" will "help keep your News Feed clear of similar stories in the future."
I believe it does. They are saving every single click and they are trying to feed you with something that you like.
From an interview of a Facebook Employee:
The Rumpus: On your servers, do you save everything ever entered into Facebook at any time, whether or not it’s been deleted, untagged, and so forth?
Facebook Employee: That is essentially correct at this moment. The only reason we’re changing that is for performance reasons. When you make any sort of interaction on Facebook — upload a photo, click on somebody’s profile, update your status, change your profile information —