Today, Apple sent an email to Mac Developers to encouraged them to get ready for Gatekeeper. “Gatekeeper is a new feature in OS X Mountain Lion that helps protect users from downloading and installing malicious software. Signing your applications, plug-ins, and installer packages with a Developer ID certificate lets Gatekeeper verify that they are not known malware and have not been tampered with. Mac Developer Program members can sign applications with their Developer ID now to get ready for Gatekeeper“.
The theory is that when Mountain Lion is released with the default setting to only install apps signed by Apple, many novice users will keep that setting and thereby only install apps from developers that Apple signed-off on.