You can also limit who gets to view a notebook by selecting different email addresses. This could be beneficial in a classroom context, when a student just wants to share access to their notebook with a few partners and the teacher, but not the entire class or the world.

Overall, however, I am VERY impressed with the Google Notebook tool and the possibilities it presents! I think it has HUGE applications for educational research, particularly because it permits such easy harvesting of links, quotations, and images with the date and originating URL/website included in the notebook clipping.