A lady that lives to my left has a camera that points toward my driveway. I usually leave the house between 5:15 and 5:30AM, and she's always reporting that someone is trying to, or has broken in to "the car next door". I've gone talked to her at her house and told her it was me, and I've repeatedly gone on Nextdoor and said, "No break in, just me leaving for work, and stop reporting it." After the twentieth time, I had to get in touch with the moderators to have them remove those posts. She is also one that just loves to stir the pot and riling people up about the HOA board. "What is the HOA doing about this?" "What are they doing about that?", and I always respond with "Why don't you attend the HOA board meeting, which is the 3rd Thursday of every month and find out?". She doesn't respond and she never attends (I know because I'm on the HOA board). I also point her to the HOA's website where all agendas, meeting minutes, schedule of events, and the progress of repairs and maintenance are posted, but she is too freakin' lazy to go look herself.
Then you have ones on Nextdoor that owe back HOA dues of over $2K (our dues are $370 a year, 1/2 paid every 6 months), and they are bitching and moaning about not getting Architectural Control Committee approval of something they want done, and the CC&Rs, etc. explicitly state that no approval will be granted until the homeowner is in good standing. But by state law, as a board member we are not allowed to "out" people for never paying their HOA dues.
There are some legitimately good stuff on Nextdoor, but I find it for the most part a total waste of time.