iTunes match wifi only?
I went out for a drive, and when I tried to play a song from my iPhone, I got the message that I needed to be connected to wifi to play songs from iTunes match.
iTunes match had not only taken all the songs off my iPod, but in addition, wouldn't play any of the songs uploaded because I only had 3G connection, no wifi, so I had NONE of my songs to listen to.
The main reason I did this iTunes match thing was have access to more songs on the road, not less.