Has anyone gone throught the list of root certificates that are trusted in the browsers/OSes and done some homework on them? Would be interesting to see what's

Has anyone gone throught the list of root certificates that are trusted in the browsers/OSes and done some homework on them? Would be interesting to see what's behind those authorities and also which certificates they have issued. I see that in the OS X keychain I have 213 "system roots" that are trusted, I wonder how many of them I really need...