John Gruber added an update to this post in which he explained that he had mixed the terms iTunes Match and iTunes in the Cloud. I think the easiest way to differentiate is as follows:

• iCloud: this is Apple’s overall cloud strategy that encompasses the ability to store application data and a media locker in the cloud;
• iTunes in the Cloud: this is the iCloud component that allows you to re-download material from your media locker. This includes books, apps, music, TV shows and (depending on where you are) movies;
• iTunes Match: this is the subscription service by which Apple allow you to music files not originally purchased from iTunes to your media locker.

Maybe it’s not 100% accurate, but it’s enough to keep it straight in my mind.