I'd rather have a "Video Viewing List" that gets video watching out of the browser. Apple is one of the few participants in the ecosystem that might have enough "market power" to do that at this late date.
I think you run into a lot more issues with copyright enforcement, storage space, and ability to even copy files (different format, might only be served in flash) than text-based services have. We might have to wait until HTML5 video grows enough in popularity before seeing a decent implementation of this feature.
That's one of the things I like about the onboarding experience with Shelby.tv; when you sign up, you can start watching what your friends are tweeting/sharing since it pulls it from you twitter/facebook accounts.
....now if only my instapaper filled up with articles that I wanted to read all by itself....
Also, the application is extremely lightweight and doesn't get in the way of the video --- a simple, yet powerful experience.