In a recent Quora answer to a question on how Facebook reached 500 million users, Andy Johns gave an in-depth look into the culture of growth at the company. Growth seems to be central to the company's strategy, with Johns going on to say that the localization of the site was 'the greatest lever' in obtaining the mass of users they accumulated.
Of course there are myriad other growth and retention tactics used that do not involve translation, but the ability of the majority of the world to access the site in their own language seems to have 'done the trick' for the folks about to float.
But what of their strategy? I questioned Johns on the crowdsourcing model, and he was good enough to reply, saying that their reliance on the community was not 100%, and that a team of professionals were editing and proofing crowdsourced translations. He also implied the sheer scale of crowdsourcing enabled them to turn around entire translated versions of the site in under 24 hours. I went on then to mention quality concerns and a few misconceptions around the task of translation.
The Q&A session is in the comments section if you'd like to read more.