Yesterday some people started a buzz around some Amazon mp3's being "watermarked". Now, please, calm down: I know that talking about watermarked songs might be good to get some readers, after the discovery of iTunes watermarks on their DRM-free songs, but not everything can be considering watermarking...
Amazon sells plain and simple mp3's, directly ripped from CD's. That means that there are no watermarks in the sound, and since there's no way in the mp3 specification of watermarking a file in another way, the only information that Amazon could possibly add to the files is the ID3 info - simply editable by almost every mp3 player out there. And yes, some Amazon mp3's (surprisingly not all) have ID3 tags telling that they were purchased in Amazon, but there's no personal info there and there's really nothing wrong in those tags. To give you a comparison term, all songs bought at amiestreet.com come, in the Comments section, "This song was downloaded from AmieStreet.com". Simmilary, all songs downloaded from last.fm have in the Comments section "Free download from www.last.fm (http://www.last.fm/)".
It gives me more nerves knowing that every last.fm downloaded track comes bad tagged (every track is tagged as being the 1st of the album, even when the last.fm website knows it is not) than knowing that Amazon's mp3's come with full tags, including a comment saying the track was purchased there.
Nothing to see here, move along.