I'm really surprised that nobody has mentioned App-V yet. I guess it's because of HN's bias towards developers rather than computing infrastructure types.
App-V encapsulates pretty much any Windows application. It prevents it from screwing up the system. It would be a good foundation for this app store - and it doesn't require that every app ever written is redone. It dummies out the registry and file system paths. The basics of this technology were used in Vista (and now Win7) to allow them to make major changes to filesystem structure without breaking compatibility with older apps. Microsoft bought this technology from Softricity years ago - http://www.microsoft.com/systemcenter/appv/default.mspx.
If you want to see what this could be like - look at http://spoon.net/browsers/ if you have a Windows PC. Stream apps from the Internet to run locally in an isolated execution environment. (BTW: Spoon doesn't run on App-V, it is an alternative).
I mentioned it elsewhere in this thread. There's a "Click-to-run" SKU of Office 2010 available running under App-V. It's (seriously) magical technology. Your application streams to you while you run it, application updates are completely transparent, and registry modifications are entirely within the App-V sandbox. There's some work that MS had to do to add hooks to allow Office 2010 to interact with the local system when necessary.
Yeah, I'm familiar with that click to run Office 2010. I think that is the start of App-V becoming more prevalent by default in Microsoft's own applications.
App-V encapsulates pretty much any Windows application. It prevents it from screwing up the system. It would be a good foundation for this app store - and it doesn't require that every app ever written is redone. It dummies out the registry and file system paths. The basics of this technology were used in Vista (and now Win7) to allow them to make major changes to filesystem structure without breaking compatibility with older apps. Microsoft bought this technology from Softricity years ago - http://www.microsoft.com/systemcenter/appv/default.mspx.
If you want to see what this could be like - look at http://spoon.net/browsers/ if you have a Windows PC. Stream apps from the Internet to run locally in an isolated execution environment. (BTW: Spoon doesn't run on App-V, it is an alternative).