It depends on which country you target. In western countries, we use mostly :
-Google +
-Facebook
-Twitter
etc
In fact, Sociaux medias is not related directly to the traffic of the website but it contribute to the web image and social image , etc...
But in China where all these famous sociaux applications are blocked, we should user the others as the alternative such as
- wechat
- weibo
- renren
- youku
etc.