It wouldn't be hard to run every submitted link through http://www.coralcdn.org/, then if the site goes down add a comment to the thread linking to their .nyud.net address (eg http://google.com.nyud.net/ )
I love Coral CDN... and could see it being a model for (or supporting-part) of a generalized cache-popular-submissions solution. But, it seems it doesn't support HTTPS sites.