Social networking offers lots of collaboration and knowledge-sharing benefits. If you've been looking for a safe, open source social networking alternative to the likes of Facebook, you should take a look at Elgg. You can set up social networks similar to Facebook, but you can have complete control over who belongs, and if content and information gets exposed over the open web or not. This means you could set up networks by project, department, or even company-wide as you see fit for the needs of your organization. Each user also has granular privacy, allowing individuals to control who sees what information about them. Because of this control, Elgg has proven popular with educators looking for a low-cost social networking tool that gives administrators control over where student content goes. Enterprise environments have similar requirements, and Elgg satisfies the needs of both settings. Check out Elgg [1]
Links:
[1] http://elgg.org/index.php