Mountain Lion now protects your contacts
Before Mountain Lion Developer Preview 2, Mac apps could access your contacts at any time, without asking for permission. You wouldn't even know it was happening. This policy is the same as the one on iOS, which recently got a lot of attention. Today's release of DP 2 removes that ability by default. When an app attempts to access contacts for the first time, the following dialog is displayed:
There is also a new area of System Preferences, under Privacy, for managing apps that have contacts access permissions:
This functionality is clearly in response to the iOS contacts issues of the past few months. It's good to see Apple taking this seriously.