I was evaluating to build a social networking site using open source stuff like Drupal, Elgg. Elgg provides out of the box functionality for a social networking site like Orkut, Hi5, Myspace, but Drupal is far more flexible. It seems Elgg is not tested and used as much as Drupal. I have been working on Drupal for a long time now and my faith on it has only increased, though, I had to make changes to the code and modules at times.

Even though, I was skeptic about Elgg, I did some initial code evaluation and installtion. But, was not satisfied and therefore, decided to go with Drupal.

Following is the list of modules, I could need to make a social networking site:

• guestbook ( equivalent to comments on profile or scraps )
• image, inline, shazamgaller: to be able to add images inline and create photo gallaries.
• invite ( allows to become member by invitation only )
• OG ( gives you groups or communities )
• cck ( let you make any type of content )
• private message ( and chat, if you want )
• mysite
• nodeprofiles (http://groups.drupal.org/profiles-as-nodes)
• event
• buddylist

Other modules, you might need:

• bbcode & wysiwyg toolbar
• captchya
• devel
• feedback
• flatforum
• flexinode
• legal

Hope, the list doesn't look long. But, it is obvious code customization iwould be required at places to suit your need and that is very power of open source comes.

From http://drupal.org/node/109248

Drupal Social Network site Q&A