If I change my iTunes music on my device through iCloud then leave WiFi I'm pretty sure the music remains on the device, so I'm not sure what you're saying here.
I expect Apple is going to blur this line between download and stream with iTunes Match in their usual elegant and cleverly misleading manner. The ambiguity in which it was all presented and remains described on their web page says it all.
It's a cloud service. At some point, to get a given non-local song to play on your device, you must connect to the cloud, then either download/store/play/save for later, or simply stream it. It's a ~5MB hit to your data plan per song (unless you're in WiFi range) no matter how you slice it. So what 's more Apple-like for a song that's not stored locally on your device but you do own "in the cloud?"
- Search the Apple Store/cloud for the song, click download, wait for it, play it, repeat for every other song you think of
- Press play in iPod from universally sync'd playlists, and when non-local song comes up, it plays from the cloud. Essentially if either you paid $1.29 for it, iTunes matches it, or you've stored it in your own 5GB iCloud, your iPod plays the full song from the store (instead of just the 90sec preview) or your own iCloud stored version.
Again, it's pretty much 6 and a half-dozen of the other, but the smoother experience is that the user "sees" all their music organized in their custom playlists as being "on" their iPod, and behind the scenes the software decides whether to play a local copy, play from the cloud, skip the song because it's not available, or display a message
"This song cannot be played because you are not connected to the internet." Storing and syncing mere KB "iTunes Library.xml" files and streaming/downloading/playing the remote files is analogous to iCal storing .ics files in the cloud but
displaying events on the local client apps.
Whether it's downloading, streaming, or some clever revolutionary magical combination with temporary local caching of the most recently played and/or next upcoming songs...at some point it is
impossible to have all your music anywhere anytime without a constant internet connection or unrealistically large local storage drive. It remains to be seen exactly how this is implemented, but it has by no means been definitively described as "manually download and keep all the music on the device." If it were just that simple, in fact, there'd be no particular advantage to that type of service over the USB syncing to an iTunes master computer we presently have, other than you could futz with your sync settings while at the coffee shop away from the computer.
To be a valuable service, iTunes Match needs to seamlessly and intelligently manage moving/playing content from the cloud onto and off of the mobile device. It's Pandora with your personal iTunes playlists as the DJ playing iTunes store/cloud music files. Surely a setting to function only while on WiFi can be included as it already is on several other features.
A pure iCloud iPhone would be the logical extreme extension of this concept.
