I'm very wary of what sort of metrics and definitions of success are used to decide whether a project is working or not. To often, the wrong metrics and definitions are used, resulting in bad managerial decisions that are based on flawed assumptions.
A couple of good posts about how metrics and definitions of success (and, therefore, business models) can work against the user: OKCupid talks about why you should never pay for online dating, and Joshua Porter points out a paragraph in one of Mike Davidson's posts which explains why companies' iPhone/iPad apps are often better than their websites. In short, on a mobile app they don't have the opportunity to finagle the user experience to artificially bump up their metrics.
In both cases, you have a situation where the metrics and definitions of success upon which the business model relies distort the user experience by forcing them to take actions which are not necessarily in their best interests. Indeed in these cases, a swift and satisfying experience for the user is damaging to the business providing it.
When you're putting together a social media project, think first about what the most beneficial outcome for your users would be. Then figure out it can form the basis of a business model (hint: your income/ROI may be orthogonal to your desired user outcome) and then how that can be measured.
Do not start with a metric, build a business model on top of it, and then force the user to have a shoddy experience for the sake of your bottom line. And yes, this applies just as much to enterprise social media as any other sort. Don't start thinking that 'number of edits' on a wiki is a definition of success, because that just means you'll push people into more pointless editing and will take your focus of signs of real success, e.g. people being able to achieve their goals more quickly and more efficiently.