It's possible Facebook uses location data for this, but I've got an alternate theories.
This happens to me often too, with much briefer encounters: mainly dates and meetups. Since I've shared similar amounts of time at the same restaurant with hundreds or thousands people with whom I had no interaction, many of who's arrival and departure times would happen by chance to line up with mine, they must be using something else. I also share a duplex-house and an office building with people who've never been inexplicably recommended on Facebook.
From these observations, I've come to think that location data has to play a very small role in Facebook's recommendation system.
Here's my best (but untested) theory to explain this: Your house-mate searched for you on Facebook, which triggered Facebook to think you might be friends.
This happens to me often too, with much briefer encounters: mainly dates and meetups. Since I've shared similar amounts of time at the same restaurant with hundreds or thousands people with whom I had no interaction, many of who's arrival and departure times would happen by chance to line up with mine, they must be using something else. I also share a duplex-house and an office building with people who've never been inexplicably recommended on Facebook.
From these observations, I've come to think that location data has to play a very small role in Facebook's recommendation system.
Here's my best (but untested) theory to explain this: Your house-mate searched for you on Facebook, which triggered Facebook to think you might be friends.