Example: Pinterest feed for Dave Winer
Now, consider the title of the actual feed. It's just Dave Winer. When an item from that feed shows up in a river there's no easy way to know if it came from Twitter, Tumblr, Foursquare, Posterous, Path, Quora or Pinterest.
Finally, I just want to say how happy I was to see that Pinterest is producing a good RSS 2.0 feed for this very fast-growing service. That means we can integrate it into the work that we're doing, and you can integrate it in work that you're doing. It becomes an input device for anything you can dream up. That's the way people should do technology.