Excellent article, a lot more "meat" than I expected, given the title and the usual level of discourse around this topic.<p>That said, I'd advocate considering starting an internal social network project using an Open Source foundation. And, if you'll indulge me a moment of self-promotion, I'll point out Fogbeam Labs' suite of projects[1] as a good place to start - especially for a firm who wants to help shape the direction of the product(s) they will be using, but don't necessarily want to be responsible for maintaining an ESN product for perpetuity.<p>The thing we believe sets our approach apart from a lot of the other ESN products out there (Yammer, Jive, etc.) is our approach to integrating business processes and workflow with the "social" aspect of the ESN. It's still very early, not everything is implemented, but some <i>really</i> awesome stuff is in the pipeline.<p>And to be fair, there are some other OSS ESN projects out there as well. There's always Elgg, and Alfresco have been adding some "social" aspects to their Document Management product.<p>[1]: <a href="http://www.fogbeam.org/" rel="nofollow">http://www.fogbeam.org/</a>