(Image courtesy of Engadget)

iTunes may rule the roost with a whopping 28 percent of the entire music business in the United States, but that doesn’t mean the Feds have to like it.

Engadget is reporting that the U.S. Department of Justice has come sniffing at Apple’s door, having “very preliminary conversation” with Cupertino regarding their dominance in the music business with iTunes. Recent NPD research puts iTunes’ share of the music business at 28 percent, which is four percent higher than it was in the first quarter of 2009.

“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,” the Engadget report reads, noting that further details are “few and far between.”

For their part, Amazon MP3 holds a tie with Walmart for second place in the NPD data, which is saying something since the big-box retailer tends to censor a lot of the music it sells in the first place.

Nobody knows if the DoJ will walk away and leave Apple alone, but from where we sit, it seems like a lot of blustering on the Feds’ part. After all, Amazon MP3 generally offers a little wider selection and lower prices, with tracks that are totally iTunes compatible -- so at least functionality and choice wise, there’s plenty of good competition for Apple’s music behemoth.