Thanks for sending on my comment, Sylvain. Here are some more ideas.

I think verifying user and project accounts should be ongoing, rather than done on a periodical basis, and done based on "need". That way inactive accounts that are needed by other users are dealt with higher priority. Creating, what I'd imagine is, a giant periodic list of inactive users or projects would be a lot of work for Administration. Let me offer an alternative.

When trying to join projects or simply send a friendly message to a user through the Savane system, sometimes emails bounce for a user or for (all) the user(s) of a project. There's currently no feedback to Savane for this situation.

Perhaps there could be a web form for users to prompt confirmation emails be sent to potentially inactive accounts. The web form could be in /users, but is only available as a URL sent by Exim with message failure (or warning) messages. The confirmation emails could be some other verification web form ("Hit submit if you're account is still active."). If after some amount of time there is no confirmation for an account, then there name gets added to some "Missing users" list. The list can centralizing a way of locating lost people, and with Administration acting to revoke accounts or free-up projects.

My proposal doesn't catch every inactive account that exists (as I argue it shouldn't), and email confirmation can create false positives, because of mail server outages or email address changes, but I think it would be a start for plugging the giant sucking sounds that can occur to project hosting web sites.

When a project is inactive, it would be good if its admins were sent a mail asking to confirm they are still in charge of the project. Activity means short delay when replying to trackers items, and CVS activity. Can be done via a cronjob.

After several months, a reminder can be sent.
After yet another several months, the admins are disabled and the project is open for takeover.

Advantages:
- when a user complains that his admin is not-responding, you may get a confirmation using these stats.
- automatically updated information in the project page, showing whether the project is maintained or not, so better understanding for users when their mails / support requests get unreplied.

Thanks to RMS for suggesting this feature.