A few days ago Socialbakers published statistics about the penetration of Facebook in terms of number of users per city (please note that you need to connect with your Facebook profile to see the whole list).
Results are quite interesting, since Caracas (Venezuela), Washington DC (USA) and Ankara (Turkey) seem to be the capital cities in the world with the highest penetration, respectively 200%, 180% and 172%. Although it is likely that there are quite a few people who work or study in these cities and are not registered residents, the disproportion is quite amazing, and clearly suggests that many people have more than one profile.
Also, looking at the same country, results are quite different. in the US, Chicago has 34% while New York a meager 21%. If somebody things that this relates to size, consider that Jakarta, which has a larger population than both, has 80%. Looking at Spain, Barcelona has 54% while Madrid has 116%.
There is no way one can make sense of these, which seems to suggest that governments should be quite careful when dealing with Facebook as if it were a real place. There are a lot of inexplicable differences here, and maybe we should all take Facebook far less seriously than we actually do.