So far we are getting very promising numbers. The main difference betwen us and all of the annotation services which have come before us (around 50 on last count, thanks to Hypothes.is), is that we are page level. We connect one URL to another. It is so simple your grandmother could probably do it. The previous versions were all line-level, meaning that you had to highlight text and then write your comment, or connect to another page etc. It was overwhelming and confusing. rbutr requires you to press two button, small descriptive comment and tag. You don't need to be an expert on the subject matter or anything. You just connect the two authors who claim to know about it to one another...