A couple years ago I bought some rural land with the idea that something like this. . . something I think of as "ecosteading" is going to become a trend of sorts. The idea that I'm working on (and have already applied to YC and a bunch of other incubators with) is actually right along this line: a platform for people to buy and sell land, exchange ideas for ecological homesteading, even build out a platform for more intelligent urban planning. When it's done from the "ground up" (literally), there are all kind of future headaches that can be avoided.
Imagine if the Hyperloop or the California high speed rail had been able to be laid down before most of the development around this insanely populated state took place. Population growth is exponential; it's inevitable that we're going to need smarter ways of transporting people and consumables. The key is figuring out where these new hubs of population are going. Like-minded people congregate; and this idea gives them a way to do it with others.
If this sounds like something interesting/exciting, I am kinda sorta looking for people to work with. Research it, tell me what you can offer (it's Rails!) and what you think of what's done so far: https://angel.co/ecosteader (email only please)