Searching around this morning, I found this insightful comment on NextDoor which echoes my concerns. It was posted on a message board way back in October 2011:
How tragic that I could sign up to *heyneighbor.com* and *not* be connected to all my neighbours who happened to signed up to *nextdoor.com* And every new venture in this space could serve to silo people as much as it connects them. These business models contain paradox – they can only succeed in a neighbourhood if they have a monopoly.
There’s a lot of truth here.