To continue to improve the overall quality and reliability of iTunes Match, we will be deleting all current iCloud libraries on Thursday, October 27th.
To prepare, please turn off iTunes Match on all of your computers and iOS devices. On your computer, choose Store > Turn off iTunes Match. On your iOS device, tap Settings > Music, then turn off iTunes Match.
The songs on your computer should not be affected. As always, please backup regularly and do not delete the music you add to iCloud from your computer.
Apple Developer Program Support
Apple says it will launch the iTunes Match service at the end of this month. On Wednesday an iTunes Match toggle was added to the Music section of the Settings app in iOS 5, also signaling that the public launch is near.