Well, it's simple whenever you write something i mean post something, you are spreading your material on social networking sites, so in return if your posts are liked (which will attract many users) then it will help you to not only get a good piece of traffic but also popularity.. Inshort, You are making "Backlinks"
Social Networking help in brand brand building and reputation to all type of business.MySpace, Orkut and Friendster grew as means to stay in touch with friends, meet new people online and to share ideas. LinkedIn has a similar slant – it is great for entrepreneurs and professionals who want to mine their contacts for hiring / outsourcing. And Flickr is just a blindingly simple tool for sharing photos.
Social network marketing works in the exact same fashion, except people choose to provide your link without being asked to do so, and places like del.ici.ous, Digg, Blogpulse, and Technorati give them the ability to do that. http://www.theecommercesolution.com/blog/2007/05/01/how-social-network-marketing-works/
alodia you are right. The benefit of del.ici.ous, digg etc. is that it is essentially only positive advertising. On other social media platforms, such as Facebook, Linkedin etc., a lot of times links that go viral are not at all always positive, i.e. last super-vira video, Friday, went viral because of how bad it was. The popularity of that video, however, did land the "singer?" an interview with Ryan Seacrest who made her talk to a top of the line manager. Bad advertising is still advertising