I love Apple since it started and been a Mac user since it came out. Much that MobileMe was frustrating and had a lousy launch, I thought it was impossible to make something worse than MobileMe. Apple succeeded with this disaster, data destroying, heart burning, stomach churning and hours wasting beast called iCloud.
See iCloud Server Error: Can't add/edit contacts + it overwrites AddressBook edits By IMRAN Happy to have your thoughts on how to solve that nightmare. My last attempt (manually restorying my 5000 contacts in AddressBook, then painfully manually deleting contacts in iCloud {Select All > Delete there gives Server Errors also}. Finally managed. Then resyncing the MacBook Pro to iCloud led to 1000 contacts NOT syncing and no way except manually listing each address list side by side to figure out which ones it missed pulling in. Horror. Disaster. Shame.
For the user who says that turning off iCloud on the Mac and accepting its offer to delete data will delete data only on the cloud, sorry, but, unless I misunderstood you, that is dangerously wrong.
Like an evil spawn of SkyNet and a PC Boot Sector Virus, once iCloud has grabbed your data IT becomes the master of your data, your digital life. Deleting stuff means the stuff on your DEVICE (e.g. MacBook Pro, where you created and have all the ORIGINAL data in that iCloud sucked in) is what will be destroyed. Be careful.
If you're playing with this beast, not only make backups of your data in AddressBook and iCal, but invest in an external drive and clone your whole hard drive.
I am literally having to make a decision tonight, keep my MacBook Pro as the master, and sync via iTunes to the iPhone 4S and 4. I have an iMac mostly for music and video, which it was "cool" to have synced iCal and AB on, though not regularly used. But, after the hours wasted with iCloud, and the repeated data loss, I can live without the iMac being a synced device.
Hope this helps.
Regards
Imran Anwar