Here's an interview with Andrew McAfee from MIT (source McKinseyquarterly), talking about organisational change, related to improving knowledge flows with social media. He reaffirmes that it works to start with thinking about the challenge you want to address and from there work towards the tools and the way of measuring changes. For instance, the US intelligence had a serious knowledge sharing and expertise location problem. Through use of wikis and blogs with good search functions, the situation was improved. Another organisation had a problem with redundancy. They created a central and accessible space to ask questions and had others answer the questions. So his main adivse is: think upfront what you want to improve with social media, don't just introduce it for the sake of introducing technology.
* Find pockets of energy and work from there
* Signal from the top what you want to achieve and want to see (eg if it's people blogging, start blogging yourself)
What can really undermine adoption processes in organisations is dumping the tools without patience and encouragement, or being too concerned about the risks.
Unfortunately I have seen a case where both has been done. However it was really hard to introduce a new way of working. I thought in that case it would have helped to see it as a change process whereby tools are just one of a series of interventions.
You might watch the whole interview, it lasts about 10 minutes