Sales of e-books on Apple's iBookstore have made "barely a blip" in the digital book market. Will its new iBooks gift cards help to change this -- or will customers continue to use apps to allow them to read Amazon and Barnes & Noble e-books on their Apple devices?
Amazon has been one of the most resilient Internet stocks. But now, with the iPod, iTunes and iPad, Apple is seriously threatening Amazon's key strength -- its control over online sales of media. That's why the tumble in Amazon's stock could mark a turning point.