Hello,
I'm encountering this same glitch.
The pages Brenden links to seem to all be focused on how to make sure iTunes can connect to the iTunes store.
I'm not sure about egglands_best, but I don't want to be constantly logged into anything that has my payment information and the ability to make purchases if I hit the wrong button (or someone using my Mac does).
Whenever I open up iTunes, this notification is the first thing I see. I hit "cancel", and the notification goes away. I close my laptop and open it back up again, and then there's the notification again. I hit "cancel" and the notification goes away. I plug in my phone to charge it up, and then there's the notification again. I hit "cancel" and the notification goes away. I try to listen to some music, and then there's the notification again. I hit "cancel" and the notification goes away. I reset my Internet connection, and then there's the notification again.
Further, if you try to ignore the notification, the iTunes icon in the dock bounces up and down infinity times until you click on it and hit the "cancel" button again. It's wildly intrusive and impossible to ignore.
How do we stop iTunes trying to log into the iTunes store?