"ALL THE WORLD'S A FROOGLE"
While Amazon has been indirectly skirmishing with traditional retailers since they started, their new move in Japan is tantamount to a direct declaration of war.
Their "Amazon Scan Search" product allows users to download a free application onto their camera-enabled mobile phone. This allows them to scan barcodes of ordinary products and then search Amazon.co.jp for it.
Not only does this allow them to make an instant price comparison, but they can decide to purchase the product instantly, from Amazon via their phone.
This puts the retail price directly in the spot light and offline retailers with their higher overhead aren't going to like it at all.
Of course, we've had price comparison products before. Originally from Scan.com (which went bust a few years ago) and more recently from Scanbuy.
However, these were independent efforts and lacked the huge marketing muscle of the mighty Amazon.
Outside of books, I can think of about a couple other billion items Amazon could offer price comparison too. Wonder what took them so long to think of this