I'm the co-founder of Workstax (<a href="http://www.workstax.com" rel="nofollow">http://www.workstax.com</a>), a service which, from the sounds of their overview, is very similar to what these folks are going to build.<p>We have taken ideas from Facebook/Twitter, Reddit, and SharePoint, to build our messaging system for teams:<p>- from FB/Twitter, we took the idea of a Feed, Profile (and explicit support for tagging)<p>- from Reddit we took the idea of voting up/down to signal to the rest of the team (but we also introduced posting quotas to counter spam, and giving you the ability to use your quota to put posts/documents at the top of the feed)<p>- from SharePoint we took ideas about teams, documents, discussion threads, and specifically worked on search to make it better than that of SharePoint.<p>We pushed these features out just last Thursday and I wrote a part 1 blog entry about it here: <a href="http://joubert.posterous.com/separating-the-important-messages-from-the-ir" rel="nofollow">http://joubert.posterous.com/separating-the-important-messag...</a>