My Contacts (accessible via Mail or the Contacts applications) are read-only on my Mac Book Pro running Mac OS X 10.8.2. Contacts reports itself as Version 7.1 (1167).
I have 5 total contacts currently, including Apple and "Me". Not sure what I did to add the other 3, but they cannot be modified or deleted, nor can I add any new ones.
If I add or edit a contact it behaves normally, until I close Contacts. When I reopen it then all the changes are gone.
I thought maybe the contacts folder was read-only in my Library, and thought I double checked that, but maybe I missed something.
The interesting thing is both the "On My Mac" and "iCloud" contacts are read-only.