By "listing-based app," I'm referring to event apps like Eventbrite and restaurant apps like Yelp.
Whereas some apps allow the user to adjust the radius being used, i.e. "I want to see all listings within [#] miles of the location I've selected," other apps, perhaps in the interest of simplicity, don't allow for this level of customization.
In these cases without customization, I assume a fixed radius is being used in all situations? I find this interesting, because a radius that makes sense in one market, e.g. a market with a lot of sprawl like Los Angeles, might not make sense in another market, e.g. a market that's a little more condensed, like New York.
(I'm interested in reading any good articles on this stuff, as well!)