I have several counter-risks here: * writing applications that ignore the known (perhaps sometimes non-trivial) best practice, which is to detect the capabilities required by the application (and which, as I discover, has been supported by the Gestalt() API since Classic OS 6.0.4) http://developer.apple.com/documentation/Darwin/Reference/Manpages/man3/Mac:... * if not using the best practice, writing applications that depend on a third point of the OS version; * if detecting a minor OS version, writing applications that refuse to run instead of displaying a warning dialogue. Having said which, the definition of MAC_OS_X_VERSION_ACTUAL does seem incredibly short-sighted. ------------------------------