Yours Truly writing at Mac.AppStorm:
When Apple announced the Mac App Store, many felt that they were pushing OS X toward a model similar to the iOS ecosystem, in other words, that Mac applications would someday be restricted only to the Mac App Store. One could certainly make the argument that this would be better in many ways for end users. For instance, if applications only came from the Mac App Store, and had to pass through the scrutiny of the app reviewers, then the end user could be assured a high degree of probability that the downloaded application is not malware.
But this model would also not be without problems. We are used to installing any third party application we please. Many called foul on the Mac App Store and warned to stay away from it. Well, at least with Mountain Lion, Apple has not taken that route. But Apple also did not sit still on this issue.
Yours truly on Gatekeeper at Mac.Appstorm. My editor changed the title to be a bit more sensational (which I’m not a huge fan of, but I see the appeal), and the first 2 paragraphs are a summary also written by my editor. Other than that, it’s my work.