It was Franco who first alerted us to the discovery of private data encoded into the supposedly DRM-free files being sold by Apple:
We now know where the extra iTunes charges for “Fairplay” tracks is going: all downloaded songs come free with personalised information like your name, email address and other account information. They must have run out of space otherwise they could have squeezed in some bank details and mother’s maiden name.
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.