Facebook is now using location to suggest potential "Friends" which just sounds like a terrible idea:
Last week, I met a man who suspected Facebook had tracked his location to figure out who he was meeting with. He was a dad who had recently attended a gathering for suicidal teens. The next morning, he told me, he opened Facebook to find that one of the anonymous parents at the gathering popped up as a “person you may know.”
By way of Bruce Schneier who also has this to say:
The article goes on to describe situations where you don't want Facebook to do this: Alcoholics Anonymous meetings, singles bars, some Tinder dates, and so on. But this is part of Facebook's aggressive use of location data in many of its services.