Is Mozilla trying to kill app stores? No -- quite the opposite. They seem intent on creating a more homogeneous environment, beneficial to developers and customers alike. Slogans like "There's an app for that" would be truer than ever if a developer could write code guaranteed to run on all big smartphone platforms without extra tweaking.
There are drawbacks, however. Online apps generally require an active Internet connection, and performance of web apps has more to do with connection speed than hardware power. Google, Microsoft and others have already acknowledged this, hence the development of "offline" web-based apps. There is no reason Mozilla can't follow their lead.
How do you think Mozilla could encourage developers to abandon existing app store models and embrace a unified environment?