Different social networks have different feature sets and perhaps their popularity in different countries reflects how well they fit local customs and social protocols. For example, Orkut became popular in Brazil entirely unexpectedly, maybe they hit a sweet spot with Brazilian culture.<p>It's surprising that Facebook does no tweaking to different cultures and it is still going so strongly worldwide. I guess this is a sign of real globalization - social norms online do not seem to vary from country to country so much.