I think its early days for QR codes, a lot of people don't know what they are although they are being seen more and more. It's a bit like 15 years ago when we started seeing WWW's crop up.
I think the scope for QR Codes is massive in some industries but can't think of any applications for the self employed carpet cleaner, maybe someone here might have some ideas. ( Ooo, just thought of one, but its a bit gimmicky!).
I think that thanks to QR Codes the cost of Smart Phones is going to go through the floor and could even be free as companies realise how they can impact on their advertising.