How about: "here" means smallest radius such that there are 10 users.
"Here" is 1 kilometer. If we allow to change the distance the purpose of the app itself will be change. The purpose is to be always in location context, if the user enter a distance of 1000KM then it becomes more like twitter.
Agreed. I'm in Maine - not many of us 'here' to begin with :)
The network effect needs to come into play and yes, one should get the opportunity to expand the geographical boundaries.