One successful version of what you're asking about seems to be the Vermont based Front Porch Forum. They have gotten some press in the last year and there was this thread about them on hackernews a while back : https://news.ycombinator.com/item?id=41208506 Whether they'd be receptive to share their secret sauce and let a thousand Front Porches bloom is another question though, guess you could ask them! :)
I've wondered how FPF has managed to pull off such an achievement. Perhaps FPF became the local standard, reaching a self-sustaining mass of users before the Facebook and Nextdoor marketing machines saturated user attention elsewhere in the country?
Having grown up nearby, there is a strong sense of roots people have out there, as well as a strong preference for local-made everything. Think of it as a rural, fairly well-educated anti-Walmart energy. It may be hard to reprodu e that environment and even harder to start something like that up once alternatives are already available.