If you were making an app store, what would the rules be?

I think the app store model is a very good one, not just for phones, but for most any sort of general-purpose consumer computing device. To have every application on the system, as well as the OS itself under a common installation/update mechanism along with a repository of software known to be non-malicious would be... a lot like a modern Linux distribution, actually. Of course, Linux distributions lack a mechanism for buying software, and many find the idea of doing so abhorrent.

If you were in charge of the app store for some new platform, be it a netbook, tablet, phone or something not yet invented, what rules would you put in place? We're all aware of the problems with Apple's approach, but we have no shining example to point to and say "that's the way".