What social networks drive the most traffic to a blog?

It depends on the area or region. In some regions like europe almost every social network would qualify or work in this case while other regions only selected ones would work, however Facebook & Twitter have proven to a success among the other social networks available in the Global village. Thanx for the invitation

LinkedIn and baty which bring education elites together are growing in driving traffic whilst Facebook looses its pace.   

Facebook is on the top of the list to drive traffic if you do a bit of advertising on it, if you just want to get traffic completely free Twitter comes next but it doesn't provide that much traffic unless you have a lot of followers 

Agreed with the experts answer.

Thank you for the invitation!

Thank you. It varies area to area. Normally facebook & twitter.

Thanks for your invitation, Agree on experts answer.