There is a lot of success social networking site out there that created using open source or commercial content management system.
You can get starting create yours social networking site by using avalaible social networking CMS. If you have enought money you can paid for commercial social network CMS. For you guys who have enought time and have passion in programming and design, you can create it yourself. In this post im not talking about how to create social networking from scratch, but i will share with you some of open sources CMS that ready for social networking site.