What happens on iCloud (ex. contacts) when multiple family members use the same Apple ID?

Question

What happens on iCloud when multiple family members use the same Apple ID?  For example if we all choose to use iCloud for contacts, are they all merged together?  We use the same Apple ID so we can use find my iPhone to keep track of the whole family.

Answer 1

Of course if you are both connected to the same iCloud account you have the same contacts - what did you expect?. The contacts live on the server and are read from there by the devices; so as you've both managed to sync your contacts up to iCloud they are now inextricably mixed. You can only delete your contacts by deleting individual ones, and doing that will delete them from your phone as well.
You can only unravel this by
1. In the iCloud contacts page at http://icloud.com, select all the contacts, click on the cogwheel icon at bottom left and choose 'Export vCard'.
2. Sign out of System Preferences>iCloud
3. Create a new Apple ID and open a new iCloud account with it for your own use.
4. Import the vCard back into the iCloud contacts page.
5. Go to http://icloud.com and sign in with the original ID. This is now his ID. Work through the contacts individually deleting the ones you don't want him to have. When done sign out and advise him to change his password.
6. Go to the new iCloud account and delete his contacts individually.
Of course if you have also been syncing calendars and using the same email address there are problems with doing this.