in order to make a better recommendation system we need to know more about individual users, including actual page to page navigation, page view history etc. We can make a reasonable recommendation system without this information, we'll call this 0. Once we know what we know about individuals and can clearly state that to them in a language they can understand we can work on what a -1 and +1 would be. -1 would be a privacy setting where users site actions don't affect any recommendation systems, and the user might not see any recommendations from the system. +1 could allow the user to opt-in to a system where their page to page navigation is tracked and stored as well as page view and edit history. This would not only allow for richer recommendations for editing and reading but also allow for things like sync'd reading positions between mobile and desktop,