Federico Viticci at Mac Stories:
As Steve Jobs confirmed at the “Back to the Mac” event, the Mac App Store will be the best way to discover and install apps, but not the only one. You’ll still be able to purchase apps directly from developers’ websites and run installers or .DMG files just fine. Can you imagine what could ever happen if Apple turned the Mac into an App Store-only “closed” system with no possibility to download software from other sources? After 20 years of regular installations?
This, without a doubt, is the scariest thing about the Mac App Store. But I really don’t see Apple pulling the trigger on closing app installation on the Mac. The outcry from developers like Microsoft and Adobe would be deafening. These companies are not going to use an App Store to publish their major software titles. Without Office and Creative Suite, the Mac would be dead in the water to a lot of people.