This is trilateration, not triangulation. Triangulation works if you know the angles, trilateration works if you know the distances and uses circles.

Source: I've done this before and it is very accurate and creepy.

> This could be mitigated by rounding off coordinates to be coarse enough that it doesn't give their precise location before calculating the distance.

Reporting a slightly different location to users or varying the search radius per user search could help.