As the largest seller of DVDs, Wal-Mart accounts for roughly 40% of the $17 billion in DVDs that will be sold this year, a financial lifeline to big-spending studios. But now Wal-Mart's video business faces a potential threat by Steve Jobs and Apple Computer (AAPL), which in mid-September, sources tell BusinessWeek, plans to announce it will start offering movie downloads from its iTunes store. More →