Tipping point
After reading this article, I'd first like to say that even the Tinder flaw seems to me to be beyond the abilities of Joe Stalker to diagnose. The people who find these flaws are really on the top of their game. Kudos to them.
That being said, that triangulation thing seems to be a bit difficult to avoid. Even if you fudge the distance a bit, you're still informing a stalker of a distance that is an easy walk away.
I think such apps should not inform of distance directly, but rather use categories like Close By, Within Driving Distance, Far Away. Category calculated on the server, obviously.
Maybe that would solve the issue ?