We have already referred to Shell in our Quantified Knowledge series. Here is a newer estimate of the value they believe KM delivers.
this 2012 story Andy Boyd talks about Shell's plans for using semantic search, and also describes the value delivered through Shell's combination of Communities of Practice and the Shell Wiki
This value figure is now $400 to $500 million per year
"Boyd calculates that Shell has so far saved €400m to €500m a year by rolling out social media tools to make it easier for employees to communicate and share ideas*. The company introduced its version of Wikipedia in 2004 following a groundswell of support from members of Shell’s online discussion forums. The system allows staff operating in remote areas of the world, where bandwidth is at a premium, to access detailed company information says Boyd. Employees are required to sign-in, which allows Shell to keep an audit trail of every change made to an article.
“We have been told that it’s the largest corporate Wiki system in the world, as big as the Polish language Wikipedia,” he said. “Our lawyers love it because they can see who said what, and all the changes. It’s a perfect record system.” Some 60,000 of Shell's 100,000 employees are active on the Wiki".Please note that "rolling out social media tools to make it easier" is rather underselling Shell's KM efforts. Shell have implemented a full Knowledge Management Framework of roles, processes, technology and governance. Social tools are one part of this, but not the whole story.