Amazon has not been forthright in releasing its sales information of its MP3 store, which opened 6 months ago. Silicon Alley Insider has reported on a rumor that Amazon has sold 27 million MP3's over that time. That means that Amazon would only have a 3-4% share on the digital music market, and an estimated revenue of only $7 million.

But that number looks to be pure conjecture, and it also comes from a biased source. The number was given by eMusic CEO David Pakman, one of Amazon's chief rivals in DRM-free MP3 tracks. He has based his number off discussions with label executives who say that eMusic is doing 3x as much business as Amazon. But keep in mind that Pakman's estimate of eMusic controlling 10-15% of the market share is also uncomfirmed, and that eMusic works exclusively with indie labels, while Amazon works with the majors.

So despite the Alley Insider's hesitancy to say so, these numbers seem to be dramatically skewed. It's quite possible, perhaps even likely, that Amazon is not doing as well as it hoped in the digital music market. But a 27 million track sales number seems absurdly low, especially when considering that Amazon sells more albums than iTunes.