At a bare minimum, showing how many edit the wiki has had over the past 12 weeks and how many forum posts/comments there has been in the past 12 weeks for a Tool will give users a good idea of how healthy the community is around that tool. Usage stats are HUGE for giving folks credit and at the same time it provides information for an efficient allocation of user effort (depending on their motivations and intentions). I haven't thought through exactly how we want to pull this off, I imagine it will become more apparent over time as we use the site ourselves, but until then, here is some food for thought.
"...if this contributor had a negative experience and was drifting away from the community – wouldn’t we want to know before they silently disappeared and moved on? This is in part the goal." http://eaves.ca/2011/04/07/developing-community-management-metrics-and-tools-for-mozilla/