iTunes is no longer allowing users to burn DRMed songs to mp3.
Daring Fireball says:

Apparently the problem only occurs when you try to rip to MP3 format, specifically – if you rip from CD back to plain (non-DRM) AAC, it still works just fine. This really sounds like a bug, not a deliberate limitation.

We know that they are leaving username and email information in the AAC headers, so it makes perfect sense to me that this would be done intentionally. There's no way Apple let's a bug like this out the door. I like that grey blog, but sometimes Gruber gives Apple the benefit of the doubt to the extreme. It seems like he's writing from the point of view of an Apple corporate advocate, not an Apple user advocate. (Disclaimer: I am an Apple shareholder, and my small business has spent ~30K this year on Apple computers).