The question of sharing is also fraught with complexity. How can one choose to share their annotations selectively — only for some works but not others, or only with some people and not others, or only in certain situations or circumstances? A book club may only want to share their annotations of the work they are discussing with each other. Similarly, users of the system trust their annotations won’t disappear if a service is sold or goes out of business. There currently isn’t a standard format for annotation exports and imports that could be used in such a scenario. As with all online services, the traditional problems of user identification and ID management is another challenge, but one that like the rest of the internet is waiting for a better ID management service.