I don't usually link to much Microsoft articles, but when I read about this, I got intrigued. Especially the possibilities that Ray Ozzie described in his blog got my attention. The spec makes it possible to keep records with multiple people. Didn't read it all, but the section "Usage Model" describes it muche better: Simple Sharing Extensions for RSS and OPML
Best of all, apparantly it's distributed under a CC license. Not the best, but at least it's something.