I'd be very surprised if it's only 70% that don't know what a green browser bar is. Fact is, the vast majority of users don't care who issued the certificate or whether it's valid; any warning dialogs will go unread and made to go away as quickly as possible. We're all doomed, I tell you.

(oo-err: "70%?" on its own isn't recognised as a valid title; bug or feature?)