Followup idea: a trusted neutral 3rd party that ranks CAs by various factors, such as controversiality. Quotes Wikipedia and other (arguably) objective sources [of fact] and welcomes debate about potential bias.
Perhaps this group could publish reports periodically so that they can then be picked up and bundled into browsers - that way you're not constantly sending [trackable] cert requests to a 3rd party, and you already have the cert info so there's no query server to DDoS.
Maybe Firefox could incorporate it into the TLS info popup and possibly the HTTPS icon... Chrome never would; this idea goes way too close to the advertising industry.
An extension would be nice, but something like this would never go viral so would never get adoption. Native browser integration would be a must.
Also, mozilla.org's cert is by DigiCert. What's their track record?