Hey, doesn't "detecting place visit at scale" answer some of the comment question seen previously on HN? I remember someone saying they visited a bar and talked to someone and that someone was "recommended friend". And this video talks about asynchronous detection of your location. It detects you're both in the same bar for a period of time and that somehow contributes to you being recommended as friends? I might be chaining too many "if" and "maybe" here though. But the video is talking about this stuff at around 31 mins.
Edit: 14 mins in or 31 mins remaining, sorry.