I might trust a certificate more if it were signed by several independent and mutually hostile authorities. Why can't my browser tell me how many independently-rooted signatures a certificate has? Why shouldn't my bank have its certificate signed by two dozen of them? Shouldn't I be notified if they had two dozen, last time I connected, and now only have two? The more sensitive the service, the more signatures I would like to see. If it takes a full minute at 100% CPU to check them all, fine. I'll put in my password when I'm satisfied, after 15 seconds, or 30, or after it's done.
We should be able to educe some sort of objective, albeit probably noisy, measure of independence, between root authorities by scanning sites.