Your approach to estimating Facebook growth by languages supported is interesting but I suspect fundamentally flawed. There's an incredible long tail when it comes to languages spoken, especially when multilingual individuals who speak both an obscure regional language and a more common one are taken into account.
http://en.wikipedia.org/wiki/List_of_languages_by_number_of_... gives a great overview of this long tail - with 70 languages, Facebook probably cover all but a few hundred million people. Simply by comparing the top 25 languages spoken with the languages Facebook support, you can see that several billion people should be able to access Facebook based on language numbers, but yet they only have 900 million users.
I strongly suspect that "working internet-enabled device available frequently" is a much better way to estimate potential Facebook adoption than language support. Having never run the numbers, though, I neither support nor refute that Facebook is running out of potential account-holders.
1. I wasn't trying to estimate Facebook's growth. I was merely trying to refute the notion that Facebook is running out of people to use their service. My method is arguably quick and dirty, but it makes for a good heuristic, doesn't it? It's enough to tell me that it's probably not worth my time to try and dig up better data.
2. Fine. The number I gave of 6910 probably was too high, but 70 is still less than half of the languages mentioned in your link. If they have 900 million users, that's less than half of the people in the world who have internet access[1]. Thus, it would seem that although there are certainly a number of problems with my approach, the evidence we have so far would seem to indicate that it did the job I intended it to do, doesn't it?
Suppose you expect Facebook to grow at 50% per year. How long until you run out of internet users?
50% for the next several years is not an outrageous expectation given their 25x sales multiple. I haven't done the math because I'm both busy and lazy, but I suspect it is actually a good bit lower than what is implied by such massive multiples.
They are indeed running out of people to sign up. On the planet. That is amazing. So amazing, I would argue, that one could imagine governments getting nervous. When's the last time you saw that in a prospectus?
They won't actually run out of course, but I expect their user growth rate to rapidly approach the low single digits. Which leaves an awful lot of innovating money extraction to provide the absurdly high valuations they've asked for and gotten. Time will tell.
http://en.wikipedia.org/wiki/List_of_languages_by_number_of_... gives a great overview of this long tail - with 70 languages, Facebook probably cover all but a few hundred million people. Simply by comparing the top 25 languages spoken with the languages Facebook support, you can see that several billion people should be able to access Facebook based on language numbers, but yet they only have 900 million users.
I strongly suspect that "working internet-enabled device available frequently" is a much better way to estimate potential Facebook adoption than language support. Having never run the numbers, though, I neither support nor refute that Facebook is running out of potential account-holders.