I think you are right about wanting to know that people you are talking to you are nearby being important. I also think if you allowed a larger radius option in the form of 10 miles or whatever, you would NEVER be able to remove it without complaints. That said, I'd consider promoting the app in a specific large city.
Alternatively, a neighborhood/borough mode might be an interesting adaption that would let you shrink as you scale. In New York, maybe you only talk to people who are also in Brooklyn. Or just Nearby parts of Brooklyn (mash up with that app that allows you to see how far you can get in a time period). In North Dakota, you might have a much much bigger region.
This would also avoid the issue I have playing a game with a geolocation based chat on android, wherein I am in the Financial district in SF, and see "nearby" people in Oakland, when I would have to cross the bridge/take bart there.
Alternatively, a neighborhood/borough mode might be an interesting adaption that would let you shrink as you scale. In New York, maybe you only talk to people who are also in Brooklyn. Or just Nearby parts of Brooklyn (mash up with that app that allows you to see how far you can get in a time period). In North Dakota, you might have a much much bigger region.
This would also avoid the issue I have playing a game with a geolocation based chat on android, wherein I am in the Financial district in SF, and see "nearby" people in Oakland, when I would have to cross the bridge/take bart there.