Facebook began gaining more traction in Japan once they setup a special office in Tokyo and let them make tweaks to the product only for the Japanese market - AFAIK, this was a unique case for them at the time, and they didn't do anything besides basic localization (which they crowdsourced...) for other nations. One of the things they did to show that they understood Japanese culture was to add a blood-type field to user profiles, a superstitious statistic that's nevertheless prevalent there. Before that, it felt too foreign.

Anecdotal but I've had many more of my Japanese and Korean friends abroad join Facebook in the last year or two.