The hypothetical process that the author describes is still a few years away at best. Google Wallet communicates with point-of-sale machines via a NFC chip, something the iPhone/Droid/Blackberry already in your pocket/purse doesn't have. Sure, the US will gradually adopt NFC (Japan is already well on their way, I believe) but it'll be a while before everyone has one in their pocket. Until then, the next best methods are Bluetooth and Wifi, both of which introduce significant security concerns when talking about financial transactions.
And then you have Barcode Scanner, which can read any barcode but can't always turn it into something meaningful. Try scanning a Hill Country Fair product next time you're at HEB; it will tell you the UPC number but won't find it in any database.
In order for something like this to really take off, each retailer is going to basically have to create their own app for shopping at their store. That app will need to interface with their entire store-specific product database, including store brands. Different stores carry different products as well, and sometimes carry the same products at different prices, so all of that will need to be accounted for. These are all huge hurdles to get over, which is why you still see a lot of retailers catering to the lowest common denominator. Hell, how many HEBs in Austin still don't offer any sort of self-checkout?
We'll probably get there eventually, but by the time we do, Google Wallet or NFC chips may have already been rendered obsolete by something better.