It would be cool if someone in the neighborhood could purchase a device that would setup a local nextdoor type of service. It would show up as a wireless connection, once connected when they try to visit a website it would give them an explanation what this service offers and allow them to setup a profile. Only people within a certain distance would be able to connect, the network could be expanded with multiple devices. It would allow, decentralized networking based on geographic location. Users would also be allowed to create a backup of their profile and interactions for record keeping if they wish.

It could be very helpful for local discussion, community awareness, emergency communication (if the access points are kept off the main grid) and possibly even direct democratic voting for small local issues.

Sort of like a PirateBox, but more sophisticated non-anonymous local private social network. Not entirely sure if the technology exists to allow this to scale affordably to at least a block or two.