Apple regarding the company's music business, wondering in particular if anything it's doing (or has done) would violate antitrust legislation. According to unnamed sources familiar with the situation, DoJ staff seem most interested in whether or not Apple's dominance in the market enabled it to unfairly prevent Amazon's music service from exclusively debuting new songs. Beyond that, details of the investigation are few and far between, but it's coincidentally coming down on Cupertino when its iTunes numbers are on the up and up. The latest NPD research figures show that over a quarter of the music purchased within the US is now procured through iTunes -- 28 percent, if you're looking for specifics, which is up 4 percentage points from Q1 2009. Meanwhile, Amazon has pulled into a tie with Walmart for second place, which may or may not coerce Wally World to ditch its morals and finally start stocking that uncensored version of My World 2.0.