It would be nice if tests leaking would actually be visible on tinderbox, as we could have avoided problems like bug 605908.
We've wanted this for some time, but there were persistent leaks at the time that nobody had fixed. I don't know what the status is right now. The harness should print out the leak log after every test, it just doesn't make anything orange at the moment. If you'd like to drive this to completion, that would be great!