[hrktb]

It is in same realm as synching datas I think. GPS is unreliable for close distances, phone clocks, user connections, the reading of the accelerometer...every little part adds fuzziness, and you have to trim down your data to get something relevant, limit the rate of false positive while allowing some leeway.

A few years ago a bunch of users in an BBS were playing with the app by bumping alone and see who the algorithm would pick as a match in their town. I guess it got better, but at that time you had something like a one in five chance to get a match in downtown areas.