Apple is planning to reset the iCloud service on September 22nd, hinting at an imminent release of an iOS 5 GM build. From 9 am PDT to 5 pm PDT during the reset, users will not be able to create or restore backups to and from iCloud. After that time, all backup data made prior to the 22nd will be erased from Apple’s servers, but a new backup will be created next time your device syncs with iCloud—so be sure not to nuke your data in that small window.
On Thursday, September 22, the iCloud Backup data will be reset. Backing up to iCloud or restoring from an iCloud backup will be unavailable from 9 AM PDT – 5 PM PDT. If you attempt a backup or restore during this time, you will receive an alert that the backup or restore was not successful. After this reset, you will be unable to restore from any backup created prior to September 22. A full backup will happen automatically the next time your device backs up to iCloud.