I think you are actually getting to the bottom of it. A combination of timestamps, and status updates, and probably that of friends tagged in the same album. Could be quite effective, as we can see.
yeah this is by far most likely. The guy's wife or whatever had her phone turned on while in labour, facebook knows her GPS coords, facebook knows she's his wife, and so on
doesnt take much to throw out a guess based on a single GPS location + timestamp. Even if the guess is only right 5% of the time it is still a profitable guess to make.
