Call me a late adopter, but I thought I'd give Google's Webmaster Tools a go. I pointed it at MtrHub and it found a bug. It found that even if you'd set a meter to be public, you still couldn't see individual reads without being logged in. It found it because if a user needs to be authorized, MtrHub returns an HTTP 401, which Webmaster Tools rightly complains about. Another advantage of using HTTP response codes conscientiously.