This is relative to the density of where you are playing. The default radius out in rural areas doesn't have enough roads, for example. A customizable radius or geofence sounds appealing.
I agree (and what you want out of the game). I wonder is there a "number of streets" which is a better sweet spot / a better default, rather than a radius
For now, I've reduced the circle radius by 20%
A geofence matching the city limits would be great
Right now there's no backend but potentially I could have a leaderboard per geofenced city / town