It's not a new concept: Many news outlets, including Poynter, have tested a service called ReadrBoard, and Quartz and Medium have notably developed their own in-the-margins commenting systems. News Genius got some attention lately for hosting an annotation-based rebuttal to Newsweek's controversial cover story on bitcoin's founder.
But Livefyre has more than 650 clients, with its social tools living on almost 100,000 sites. With that kind of scale, it hopes Sidenotes can be adopted quickly across the Web. (more...)