Several of mine have been mentioned already, like vague booking and sharing false info without fact checking.
I like to use Facebook to keep up with people, both those that I know well and especially those that I don't have the opportunity to interact with on a day-to-day basis. But...
-- People who share things ALL the time. I have a couple of people on my feed (usually older) who seem to think that if a meme says "Share this." that it means that you *must.* "Share this is you've ever used a rotary telephone!" "Share if you support our troops." "If you think all children deserve love, share this!" I also have several people on my feed who share their own posts a lot, and I'm not sure why they do that?
-- I have a couple people who go on posting binges, usually about stuff I don't care about. I know one guy who seems to live post when his favorite team is one. I can log on and my whole feed is "OMG! Did you see that? So awesome." and "Are these refs smoking something?" and "Jackson for MVP! Oh yeah!"
-- And finally, and this is reserved for the people that I know pretty well... but when I know the reality does not match the Facebook post. Examples: The friend who is seriously considering leaving her husband who posts "I love him so much." and "My husband is my best friend' posts. The mom I know is having a horrible time with her son -- failing classes, getting into trouble, disrespectful at home -- who posts about what an amazing, kind, generous, thoughtful person he is and how lucky she feels to be his mom. Or, another friend who will brag about her daughter's accomplishments and embellish, embellish, embellish. (Once, she bragged about how amazing her daughter was at track. She's just in awe, etc. She cropped a photo *i* took. In the post, it looks like her daughter came in first place, but really, she was second-to-last. She just cropped out all the other runners who were ahead. Why would she do that?) I don't air my dirty laundry on Facebook either, but I don't lie/fake things. (If it was my son who was being a jerk, I wouldn't necessarily tell everyone on FB about it, but I also wouldn't describe him as the sweetest, kindest, most loving child in the world on Facebook either. There is the option of not saying anything.) Maybe lots of other people flat out lie on FB too, but I don't know them well enough to know that they're lying.
I could unfriend/unfollow these people but all of them do post things that I'm interested in. They just ALSO post stuff I don't like. I wish Facebook would let you set up filter words for posts or something. "If it includes ____, ____, or ___. Hide it."