Yeah, the trusted/untrusted barrier is obviously a big issue. But actually Prism doesn’t give the applications any extra privileges, AFAIK. It just gives the app it’s own window and icon.

Giving the applications extra privileges is a whole new can of worms, and obviously requires the application to be modified. So does working offline. I think that Prism is initially targetting “always online” web apps, but in the future, I could imagine support for accessing local storage, and working offine.

One of the biggest problems facing the user experience of Prism is that we needed some way of magically scaling favicons to the size of desktop icons

I would have thought a much larger problem would be policing the trusted/untrusted barrier. If the user follow a link in a webapp to a site outside of the app, how does the user know that they’ve left the trusted world of the webapp, and entered the untrusted world of the Nettertubes? If your answer is to say everything site above the “mail.google.com” domain is trusted, how do you deal with distributed web-apps (like what Drupal wants to be with its single sign-on).

The idea is nice, and it seems similar to Adobe’s AIR. We just need standards to provide rich interfaces to users. As much as I dislike drag-n-drop, I’d love to see a right click for webapps.