You have to keep in mind that Japan is not like the US and even EU when it comes to phone and internet usage. My in-laws are still on a dial up that charges by the minute, but the cell phone has free internet.
Lots of ads have cell phone internet addresses on them that allow you to buy it on the spot and have it delivered.
Credit cards are still not universally accepted or trusted, so many Japanese consumers prefer to buy things on their phone and pay for it on their phonebill.
Another example of why this makes total sense in Japan and leaves most US Mac users scratching their heads: Three years ago Tsutaya (Japan's equivalent of Blockbuster) had a fully operational system in place that could figure out when you were getting out of the subway on your way home and SMS you a coupon for a specific movie that matched your renting habits. You could then order it on the phone and just pick it up at the front counter or show your phone at checkout for the discount. Not a generic spam at a certain time of day, but knowing when YOU were on your to YOUR home and what movie you would most likely want to rent. And unlike us, this wasn't an invasion of privacy or Big Brother, but a real cool convenience.
That Apple is only now launching a mobile phone commerce site is kind of surprising in that I would have thought they would have had this available years ago.