Ugh, I'm having the same problem! Created an account here just so I could post.
I added and purchased a bunch of music via my Wish List a week or two ago, and added an album in the last week. Just went to try and add more, but the "Add to Wish List" option is gone. I can still access the Wish List through the "My Wish List" link at the bottom of the store under "Manage," but can't add anything to the list. So frustrating! Why would they remove this option? Especially around Christmas?
So the only way to purchase songs and albums now is individually, through the "Buy" option, with each song or album appearing as a separate transaction? Because that is ridiculous! The "Wish List" basically functioned as a shopping cart. Is there no similar replacement?
I'm using iTunes 9.2.1 (5) on an older Mac Mini running OS 10.4.11. But like I said, the Wish List function was working fine a week or so ago. I just want to be able to use it again! Not sure I'll buy anything else from iTunes if from now on I have to buy each song or album individually. What a pain.
Anyhow, thanks in advance for any tips on fixing this. And thanks to the person who submitted feedback to Apple that links back to this thread.