Recently some friends and I noticed weird behavior by Facebook:

seeing stories by pages you haven’t “liked” just because a friend likes them (but the friend hasn’t liked the particular story). E.g. “Check pictures from our promotion” by a brand you don’t like, but your friends do.

setting pictures and statuses by friends of your friends. “The baby is born!” by a person you only have one friend in common.

getting notifications from events you are invited to, but haven’t RSVP’d. “X Posted in the Y event”.

This adds a lot of noise, and things that you most certainly are not interested in. It is said that Mark approves all these changes to the news feed, and if that’s the case (and not some random bugs crawling in), we might see even more noise. I don’t say experimenting is bad per-se, but showing obviously irrelevant information is not a good thing. Probably they are A/B testing it, verifying if there is lower interaction with these stories, and will revert the change. I hope this happens soon, because I just saw a profile picture of somebody I’ve never seen at the top of my news feed.