The app and website seem like a good idea at first. Then you get to know your neighbors. NextDoor has its share of garage sale items, and swim team meet details, but there's an ugly side. Every person "who looks out of place" walking on the sidewalk gets called out on the app. God help you if you're black and knocking on doors in our neighborhood.
The app sends "push notifications" for urgent alerts tagged as "Crime & Safety". This means that every bored, stupid Desperate Housewife who gins up a fantasy of danger now has the ability to push her stupid blather straight to your cell phone.
Case in point: This Tuesday, after a Memorial Day party at the clubhouse. The remnants of a water balloon fight were spotted by an especially stupid, fearful neighbor who posted about our "SCARY" "black tar heroine[sic]" problem.
If you think you hate your neighbors, but want to be totally sure about it, get this app or visit the website. You will never doubt how much you hate them again.