Social Network is not very helpful for internet marketing

We, AdvGen, are managing a lot of local and IT news portals. I found the most of traffic are coming from the search engines, the traditional way. Yes, the segment of Social Network traffic is getting more comparing 3 years ago. That is not as powerful as some internet marketing said. They said the social network can get your website to be well known.
If you ask me, whether that is a good idea to use Social Networks for internet marketing. I must say "Yes". That is a good tool to bring some traffic and get other people to know your website. But you need to do SEO. You cannot only rely on Social Networks.