From hypothes.is:

Hypothes.is will be a distributed, open-source platform for the collaborative evaluation of information. It will enable sentence-level critique of written words combined with a sophisticated yet easy-to-use model of community peer-review. It will work as an overlay on top of any stable content, including news, blogs, scientific articles, books, terms of service, ballot initiatives, legislation and regulations, software code and more-without requiring participation of the underlying site.

It is based on a new draft standard for annotating digital documents currently being developed by the Open Annotation Collaboration, a consortium that includes the Internet Archive, NISO (National Information Standards Organization), O’Reilly Books, Amazon, Barnes and Noble, and a number of academic institutions.

Interesting!