The web is a publishing platform. First things first, we should get our semantics right, just like we expect a book publisher to do.
Over and over again, I get designers telling me "this is a h4, and the following text is a h3". You cannot place a h3 inside a h4. Let's nation-build.
Who's responsibility is it to know about the site's information hierarchy? The designer's? The developer's? I believe everyone's.