In raising some legitimate concerns about walled gardens being created on the internet Tim Berners-Lee says the following:

You can’t make a link to any information in the iTunes world — a song or information about a band. You can’t send that link to someone else to see. You are no longer on the Web. The iTunes world is centralized and walled off.

Except it appears that you can.
For example, and this is not an endorsement of this song, here is a link to Kush by Dr. Dre.
It sure looks to me like I can link to information about a song and send that link to someone else to see.
There may be other walled garden issues with iTunes but this does not appear to be one of them.
What am I missing?