The thing is, each neighborhood has it's own content ecosystem that probably takes much time, money, and sheer effort to build up. It's not like Facebook where

The thing is, each neighborhood has it's own content ecosystem that probably takes much time, money, and sheer effort to build up. It's not like Facebook where the network builds on top of itself once it's let loose. There's no "global virality" like FB or Twitter but that's probably a feature by design. The upside I can see with this is that it's incredibly difficult to replicate what Nextdoor have created and that probably plays a part in why it's now so valuable. I mean the stickyness of a network like this is insane. It's easy for a WhatsApp or SnapChat to come in, ride off of users' contacts or address-book and build massive social networks to compete with Facebook. How the hell can you compete with what Nextdoor is doing without a significant investment of time, resources, and just grinding it out. To me, this looks like a classic example of "Doing Things That Don't Scale" and a company benefiting tremendously from it.