Heh. I sense that a proposal that doesn't have strong backing from any of the Big Ds is not going to progress very far. I'm holding out hope that Dan will weigh in. ;-) In seriousness, here's why I think it's worth doing:
Making use of a tool that's designed to inform decisions across the movement with data is awesome, and we want to see positive feedback loops where more uses of the tool encourage .. more uses of the tool. When folks see WLM using WikiMetrics, they'll want to use it for their event, or their next online campaign. It could help us create a greater sense of seriousness about data. It's not so much about accountability (checkuser-style) but visibility (recentchanges-style) which can increase adoption.
With regard to legal issues, I'm not convinced that exposing a simple cohort name like "Berlin Editathon" triggers the kinds of issues we've discussed with Luis, but we should certainly get signoff if we do this. The privacy issues potentially come into play when we disclose cohort _membership_, but cohort names should be pretty low-risk. What's the kind of exposure you're worried about?
With regard to abuse, wouldn't a simple "block this user and flag these log entries as hidden" feature take care of that? And it seems to me we'd like to have the blocking capability anyway to deal with abuse.
Anyway, I don't mean to make a huge deal of it - I think it'd be a nice touch, and help encourage use of tool by creating greater visibility for the community.