http://superuser.com/faqhttps://superuser.com/faq has some of the answers you seek. (The last 2, to be specific.)
About openID... it's much more convenient to have one login for everything, rather than lots and lots for every site, don't you think? You can make an account on Stack Exchange, that's the closest thing to a SU account and bonus, it'll work if you get a question migrated to another SE site! See: Why can't I register on SuperUser without OpenID?