This is sort of a philosophical question. Should there be rules enforcing good behavior or should the community enforce good behavior? This is a fundamental divide between people that extends to many areas more important than forums.
I, personally, am all in favor of community enforcement. First off, we do have a strong community here. I joined not too long ago, and have taken a pretty active role in trying to enforce community standards. Flag and vote for deletion non-constructive posts, comment on answers that aren't up to muster, ensure that I comment when I vote to close, and leave nasty comments when I see close vote with no comment.
I am not the only one doing this stuff. Frostfyre and Molot, for two examples, were doing this when I first joined (and still are) and their frequent commenting help me as a new user understand the site 'culture' to the point that I can now help enforce it. In turn, newer users like Secespitus and Mrkvicka are now doing the same thing.
Look at the editors tab. People like SRM, Zxyrra, and Brythan do a lot of work keeping the site tidy and organized, as have the people with the deputy badge. This is all the work that goes on 'behind the scenes' so to speak, and isn't strictly reflected in reputation.
Moral of the story: we don't need rules in place to make this site what we (the users) want it to be. It just takes some dedication. We, collectively, by our actions, can discourage the kind of bad behavior we don't want to see, like offensive questions, comments as answers, and un-commented close and downvotes.