Link Building

I wonder if link building in websites really increase the traffic and hits of a site or blog and would it increase earnings as far as advertising is concerned. A lot of websites and other SEO companies are offering services that do just the trick of seo link vine. But would it really help? As far as increasing traffic is concerned, I guess it would. A high traffic site might be the ones that direct advertisers need. However, it would probably not make a big difference if your ads are served my a mediating company like google adsense or infolinks.