Whatever you use to automatically determine my location doesn't quite get it right; it thinks that I am in a small town that I vaguely recall as not being that far away from where I now live, so it's not the biggest deal.

Also, you may want to set distances to metric for people in countries where that's the standard. It's not at all impossible to get some users in e.g. Northern European countries without translating into the local language, but the size of a mile is not something people around here tend to be familiar with.