I respectfully disagree, James.
I have my qr code front-and-center on my main site for at least 3 reasons:
1. raise the awareness of the technology in proper contexts - my site is all about mobile web, and the code is a mobile web technology
2. It is a seamless and elegant way to make the website portable to the phones, as an item in the browser and reader history - user need not retype or search for URL when wanting to revisit the site on the mobile device
3. My portfolio consists of mostly mobile web user experiences, and I want my audience to start seeing and using my mobile sites immediately - the main website acts as a conduit for that experience by providing the scanning option as the user gets to the main site
This is not an obvious use of the code, so I understand your point; but the way I am using it on my site makes it of real utility for me and my business