When will iTunes replace Wal-Mart as No. 1 music retailer? Interesting question right? Well that’s also the hot topic for discussion numerous sites and journals. According to Cnet Apple’s iTunes will likely whip past Wal-Mart Stores to become the largest U.S. music retailer sometime this year.

The NPD Group issued a report Tuesday that said Apple had outpaced Best Buy and Target to become the No. 2 U.S. music retailer. Unless the downward trend in CD sales suddenly reverses, Apple will be No. 1, said Russ Crupnick, the NPD Group’s president of Music.

“Digital sales were up close to 50 percent and CD sales were down 20 percent last year,” Crupnick said. “Even at half that growth rate in digital sales, Apple will in all likelihood catch Wal-Mart this year.”

Anybody in their teens or early 20s is going to ask, “So what else is new?” To them, digital downloads has been part of their lives for years. It’s only natural that a download store emerge as the top seller.

But anybody older is going to remember that it wasn’t too long ago when music buying meant flipping through CD racks at the former retail powerhouses, Sam Goody and Tower Records.