http://news.ycombinator.com/item?id=3882489 is misleadingly titled.
"Mac OS X 10.8 restricted to App Store, signed apps by default"
Says an App has to be released via the Appstore and signed to be installable under the default settings. This is not true. An app needs to be Signed OR in the Appstore to be installable by default.
Can you please edit your post title to include the word OR or a "/" between the two mechanisms?