A person too busy not to watch T.V does not use social networks as well i guess. The people who are free enough to use those social networking sites have time to watch a little T.V as well. Though both of them can be good sources to advertise bitcoin, the difference is that if it is being advertised on T.V, there is a possibility that it might just be shown within a country as there are channels that are just broadcasted within a country, and social networks are universal.