I'm curious as to how an App Store indicates the coming armageddon of a "locked down Mac". It will not be the only place to get Mac software (said right in the keynote). The majority of Mac buyers are the Mom, Pop and arty university student base, who really don't know of the existence of most Mac software. As a developer, a storefront for my software built right into the desktop of every new Mac sold is hardly going to be a bad thing - I get millions of eyeballs and potential one click customers for a 30% cut. If I don't like those terms, I can use the traditional distribution methods.
Now, if you're going into hypotheticals, they *might* in the future remove the traditional distribution, thus breaking all software that all their customers have ever bought for earlier versions of the Mac, and alienating every big developer out there that currently publish on the platform (Microsoft, Valve, AutoCAD, etc). But then, *gasp*, MS have an app store in Windows Phone 7 - they might do the same for Windows 8! And Google, they've pulled items from the Android store in the past - they might suddenly require that all developers submit to DNA testing! We can sit and come up with nonsensical predictions, that have limited grounding in reality and no grounding in basic business sense, forever. If Apple eventually "lock down the Mac", well, then I'll switch to Linux. Until then, hyperbole about what "might" happen, despite there being no evidence of it, is just stupid.