OS X Mountain Lion Users: No More Security Updates?

Summary: Have you not yet updated to OS X Mavericks? You better get on the ball because it appears, counter to prior practice, Apple won't be providing security updates to earlier versions anymore.

[UPDATE: An Apple spokesperson told ZDNet the company has not changed its update policy but said some older OS X versions go unpatched for architectural reasons. Apple declined to respond to a request for more details about their security update policy or for when the most recently disclosed vulnerabilities would be patched in Mountain Lion.]

Has Apple changed their policy on security updates for versions of OS X older than the current one? Apple has no documented policy on supplying such updates, but they do have a history and it seems that their actions since the release of OS X Mavericks indicate a change.