Today Facebook announced that it now has over 500 million registered users, an increase of some 100 million in the last five months, and of 400 million in the last two years. Mark Zuckerberg has already told us that it is "almost guaranteed" that the site will eventually reach a billion users, but with no indication of when he thinks that might happen.

Facebook has managed to ride out the storm of the recent privacy controversy, and it has almost become accepted wisdom that users have little expectation of privacy so one has to admire their approach of pushing the envelope of what is acceptable and then pulling back by a fraction. Take a mile and give an inch is working for Facebook, and no mistake.

So what lessons should we take from this announcement? We would suggest three key takeaways:

  • the easy growth in Facebook’s English-speaking audience has probably peaked;
  • the test for Facebook moving forward will increasingly be to achieve the same levels of penetration into emerging markets such as China, Brazil and India.
  • online marketers with international brands need to develop multi-lingual social media capabilities if they are not to see market share eroded over time.