I met a really awesome girl at a club in Hiroshima, Japan a few months ago. I didn't speak Japanese, she didn't speak English, but as luck would have it, we both spoke Spanish.
Before I left the club she asked me if we could keep in touch through Orkut. She'd never heard of Facebook. This exchange got me thinking about the regional popularity of social networks. The girl I met just happened to be half Japanese and half Brazilian. Orkut is extremely popular in Brazil so it isn't surprising that she uses it to communicate with her family members.
In the US, my home country, Facebook is extremely popular. What are some popular social networks in your country/region?