Banning Guests

And in the area of other odd developments, go manipulation of forms to make it so admins can't read the board!
Obviously, neither of these are very serious (you'd need admin access to do any of them, and hopefully you don't have untrustworthy admins) but are probably worth fixing (if a hacker gets admin, locking out all Guests and then messing up all the group stats would be annoying to say the least: of course, if you have the DB plugin they could do much worse).