As background: We found in our study that Yammer has been adopted by Deloitte primarily as a channel for creating context and awareness (to know what’s going on in the business), for information sharing, problem-solving and crowdsourcing of ideas, but not for project management, task coordination or working on joint content objects (such as on Yammer pages).
Now in my view the answer is simple:
The fact that we do not see much “real work” (e.g. working on a content object or task coordination), is not despite, but because they are a mature Yammer network! Since Deloitte have adopted Yammer at a time when no pages etc existed they have naturally adopted it as an awareness channel. Therefore, Yammer is not (yet) seen as a place to do work, but as a place to learn what’s going on within the wider organisation. Also another reason is that they are a large business, so the primary value of Yammer is in creating awareness for what’s going on beyond one’s own division (silo!).
Generally, it is much more likely for organisations to take on board these new features during initial adoption when people experiment with the new technology, new practice emerge and when it is yet to be determined what Yammer will become in that particular organisation.
Riemer, Kai; Scifleet, Paul; Reddig, Ruwen (2012): Powercrowd: Enterprise Social Networking in Professional Service Work: A Case Study of Yammer at Deloitte Australia, Sydney University Working Paper: http://hdl.handle.net/2123/8352 (download the full pdf from this site).