Firefox's live bookmarks aren't very useful to me as a general feed reader (i.e. reading news), but what if sites used them to synchronize my bookmarks? For example, I might have lists of live bookmarks for my individual to do lists, Writely documents, Bloglines folders, Google spreadsheets, and even AdWords campaigns. If I add a new item through a given site, a direct link would automatically show up in my bookmarks so I no longer have to go to the site's home page and manually navigate.
Update: Writely already supports this! Now, how about Bla-bla List or Ta-da Lists?