I suppose if image recognition was good enough, there would be no need for QR codes? You could just photograph the url and the phone would act accordingly.
A disadvantage of QR codes might be that they don't work so well for human brains: if you want to establish your brand through an advertising campaign, a QR code alone won't help much.
Excuse my French, what's QR?
QR codes work so much better, particularly for print such as the free commuter newspapers Murdoch gives to train travelers etc. The main problem is user acceptance/education outside of Japan & Korea. We did a small sample test (unscientific) with QR codes in Melbourne, AU: In the under 40s bracket, perhaps 1/15 could identify the QR code but only 1/25 could successfully use it.