Oversharing.
But since we are talking about FB pet peeves:
1. The friend that posts a selfie of herself immediately after working out...sweaty and red-faced with an update in the notes about how long her workout is
2. The cousin who spent 9 months giving a blow by blow account of her separation and and divorce.
3. The neighbor that posts a picture of her one 10 year old kid making the weirdest faces or sleeping, with the caption "My World" every day. It's a nice thought, but her BIL finally answered "tell us something we don't know" LOL and she responded "It's my FB wal, I can post whatever I want", and he said "Agreed, but it would be nice to see an update or something about him, like 'J hit a home run today!' or 'We had tons of fun at the pool, now he's exhausted', or something more than just 'My World'" LOL She posted "My World" a couple more times, just to show him that she could, I assume, and hasn't done it again.
4. The preachy one or motivation quote person who, if you know them well enough, you know that it is a thinly-veiled attempt to passively-aggressively tell someone they hate them lol
5. The one that starts attacking you because of something you post. I posted something once about my 1st grader and his friend deciding to walk home instead of go to the babysitter's car without telling anyone, and the babysitter, school, etc put out a mass alert, so the police were all over looking for the boys, found them, and brought them back to the school in the police cruiser. No pics, of course (the babysitter was in that hugely relieved/pissed off as could be stage with the boys! and didn't even THINK about taking pics.) Later she sent me something about it on FB and my BIL jumped in and said that parents are way too overprotective and when HE was young, blah, blah, blah...and *his* kid...yadda. yadda" - pretty much attacking my parenting with everything he said.
I don't give FB friends a second chance. If I don't want to see a gazillion "cause" posts, political rants, complaints, etc, I hide their newsfeeds. If someone attacks me, causes drama, tries to start a fight with me, or tries to publicly embarrass me, they are blocked for good. Like in the case of BIL, even family. If they don't like it, too bad. FB shouldn't be the only way families tell each other exactly what they think. That's what Christmas dinner is for.