Site’s worldwide expansion buzz at an all-time high, but local social networks in Russia still hold on to their lead

Facebook may be the world’s largest social network, with a user base predicted to top 837 million in 2012, according to eMarketer estimates, but the social giant isn’t the leader everywhere; it still trails local incumbents in several emerging markets, including Russia.

According to data from comScore, in October 2011, Facebook was the fourth most popular social network in Russia, reaching just over 20% of internet users in the country. It trailed three domestic sites: VKontakte (VT), Odnoklassniki.ru and Mail.ru (My World).

In addition to dominating Russia in total reach, the top two native social networks dwarfed Facebook by more than 10 to one in average time spent per user.

eMarketer forecasts the number of Facebook users in Russia will increase 62% in 2012, whereas overall social network user growth in the country is only predicted to rise 11.1%. The figures suggest that local social networks will not be able to hold onto their dominance much longer. The real question may not be whether Facebook will overtake local social networks there, but when.

For more information on social network user behavior and trends outside the US, watch for a forthcoming eMarketer report on worldwide social network usage.