A key advantage, I think, of the first approach (Sandstorm's, in theory) is in the capability of apps to run 24/7 and do useful stuff in the background, non-int

A key advantage, I think, of the first approach (Sandstorm's, in theory) is in the capability of apps to run 24/7 and do useful stuff in the background, non-interactively, when the user is offline. Like receive network messages, pull rss feeds, crawl the web on your behalf, or make your idle server's computing power available to your friends.