Big social networks put many websites out of business: anyone can create a group, say, on Facebook, and it’s much easier than to build and support whole Joomla website.
Now we want to get Joomla! web-masters back into the game, arming them with the same functionality major social networks have.
The GRA4 Social Network Extension for Joomla empowers your Joomla website with Social Networking features.
Joomla Social Network Demo: http://joomla.ucq.me/gra4/activity
Free hosting with auto-installer (Joomla supported): http://ucq.me
After single 2-minute-long installation your Joomla website will have social features likes, friends, groups, blogs, messaging, activity stream, market, events and much more.
Wiki: http://en.wiki.gra4.com/Category:Webmaster_guide
Before you install this Joomla Extension, please make sure you are installing the newest version:  http://gra4.com/file/group/96/all
For the older Joomla! versions look for Extension v.0.0.1.0

GRA4 Social Network for Joomla! Web Site