When Dassault Systemes launched DraftSight, it made sure it had the Social.
When PTC launched Creo, it made sure it had the Social.
Other CAD vendors spend on having staff and Web resources for the Social, also.
(By "the Social" I mean the Social Web, the whole Twitter, Facebook, texting thing.) Here's the problem. The Social is mobile. Social networking relocated to the smartphone a year or so ago, because the desktop is static (locked onto the desktop, like a landline rotary telephone) and smartphones are our new notebook computers.
CAD doesn't work on phones, so CAD vendors don't need the Social.
(In any case, for CAD vendors it's not about the Social, if you hadn't guessed yet; it's for the marketing.)
PS: The inspiration for this post comes from Robert Scobal's Does RockMelt (a new social browser coming tomorrow) have the right startup philosophy?