One FUD issue some people keep regurgitating to keep us from being included in browsers is they worry about us issuing certificates for the likes of paypal.com, most people pushing this line tend to neglect to mention that issuing a certificate on it’s own is mostly useless, unless you can attack the host file on a users computer or the DNS name system, in which case there is bigger problems then falsely issued SSL certificates, especially since most phishing attacks (which is the assumption likely to abuse this) don’t even resort to using SSL.
Currently we require people to have code signing access before issuing IDN/punycode domain/email certificates, and it has been suggested that we have a similar requirement for anyone requesting certificates for high profile sites.
One way to determine popularity is by sites like alexa.com which give out rankings.
I guess the question is how popular must a site be if we want to enforce this, and over what time period?
Another concern is with large organisations as a lot of departments inside these organisations run their own sub-domain and the TLD is handled usually by the main IT department, and this could be cause for concern if someone registers the TLD and starts getting certificates for either the entire organisation or for sub-domains they shouldn’t be allowed to control, this is usually controlled by an organisations IT policy, but this call also lead to someone intercepting traffic by setting up a reverse proxy, and there is questions hanging over this as it will potentially effect legit users one way or another.