I believe I've explained before that my definition of brilliant is when something that would have never occured to you becomes, after you've heard/seen it explained, so obvious that you'll never be able to go back to thinking the way you once did. This is that.

Bray is right that releasing the source code to these apps would be unlikely to hurt Apple competitively against Windows or Linux, but he overlooks another form of competition: existing versions of Mac OS X. The role these apps play isn’t just to make Mac OS X look good compared to Windows or Linux, but also to help make each new version of Mac OS X look better than the previous one; i.e. to convince Mac users that it’s worth paying for the latest upgrade.

More over at Daring Fireball.