I don't disagree with you at all; I just think that in the appliance-computing future where your computer is basically a toaster, the vast majority of users (ie, potential software customers) won't care about the "missing" apps at all. It's not a coincidence that most of the apps running up against sandboxing are tools aimed at power users -- third-party email clients, application launchers, BBEdit, backup tools, etc. These are specialized apps for users on the thin end of the bell curve. I don't think Apple cares much if they lose all the people who care about third-party text editors if they're able to start selling computers to millions of other ordinary people who have heretofore been terrified of installing software on their computers.
I'm not happy about it either; I guess I just understand what Apple's trying to do, and why Microsoft seems so eager to follow suit by setting up its own store. The "you have to be a computer guy to use computers" era is almost over.
Other developers will happily come along, work within Apple's guidelines, and sell to the giant slice of the pie chart. It's obviously a radically different model of software development, and one that's probably far less appealing to current developers, but that's what happens when industries change. The incumbents never like it.
The same thing's coming to Windows, too, thanks to the Windows Store. The whole industry's headed toward appliance computing. Maybe you can sell software to Linux users.
For ordinary customers, software that's not on the Mac App Store might as well not even exist. Developers who try to make a living selling serial numbers on the web via Paypal are going to be selling to a tinier and tinier slice of the market. We're headed toward appliance computing for almost everybody and a Linux box for the rest of us.
Apple understands this; hell, even Microsoft is starting to understand this. Does anyone doubt that we're headed in the same general direction on the Windows Store?
The neckbeards will buy from the developer. The ordinary customers Apple has been relentlessly targeting for a decade will buy from the Mac App Store. Which group is bigger?
This app is a great concept, but it's going to be interesting to see whether I'll let myself trust it enough to be useful. If I end up double-checking behind it anyway, then there's no point.