Nextdoor and Buy Nothing

Nextdoor solved the problem of knowing who lives near you without actually having to knock on doors. Buy Nothing groups running inside it turned neighborhood proximity into a functional sharing network. The app matches you with a hyperlocal feed based on your address. When someone 3 blocks away posts a free bookshelf, you see it before anyone outside the neighborhood does. Simple enough that people who don't usually post on social media still use it. That's how my neighbor, maybe 70 years old, posted a working KitchenAid mixer she didn't want anymore. It was gone in 12 minutes.