It was Franco who first alerted us to the discovery of private data encoded into the supposedly DRM-free files being sold by Apple:
Although it turns out to be even worse than that: all iTunes sales have this data encoded into them, but since the standard version is locked to a limited number of machines and players, it's caused less concern.
Ars Technica ponders why they'd bother with this ugly, embarrassing encumbrance - as it points out, the people who'd shell out a dollar for a tune aren't going to be the sort fishing in file-sharing networks anyway. It speculates there's a chance that the information might be collated for a fascinating study rather than copyright whoop-ass, but Apple are keeping quiet about what the hell they're up to for now. It all looks a little tawdry.