There's a lot more than 1 - 2 million songs per day listened to on iTunes.
If all Amazon's transactions are purchases, and Itunes is supposedly tracking songs listened to by itunes users, I'd say swise is correct that the amount of data Apple would need to store is greater.

Of course, that's a false argument, since Amazon stores much more than purchases. Amazon also stores every item you look at on their website, as well as stuff customers review or rank. They do this, at least in part, for the same reason Apple is collecting this data. To generate recommendations and sell you more stuff.

While I would not refer to this volume of data as peanuts, it's certainly possible to store it all. You could even do it with pretty Apple machines, since Oracle is now available on OSX.

The whole DRM record industry argument made by Somewhere Over the Atlantic is, in my opinion, silly. A list of IP addresses that listened to non-DRM music isn't particularly useful. The more interesting data would be "people who listen to x also listen to y". That data's more useful to retailers (like Apple), then to record companies, though.

If you're worried about this, turn the ministore off. Then itunes stops sending data, except to do CD lookups at CDDB.