It seems like the OS is either defaulting to allowing only only App Store applications or at least only (Apple-)signed applications: http://www.apple.com/macosx/mountain-lion/security.html It's still possible to turn this off, but I have a feeling that we should enjoy our freedom to run GNU grep instead of BSD grep for as long as it lasts.
This is a scary preview of Apple's vision of desktop computing (which we all anticipated with the App Store being brought over from the iPhone world to the desktop): The safest place to find apps for your Mac is the Mac App Store. That’s because the developers who create them are known to Apple, and the apps are carefully reviewed before they’re accepted in the store. As I've had no reason to upgrade my home PC from…
Carefully reviewed to ensure they don't upload your whole address book.