User Interaction Consultation/Bookmarks/read later

Brief Description
Readers should be able to bookmark articles or add them to a "read later" list. The lists could be organized around topics the reader is currently researching. Apart from articles it is also possible to include snippets from the text, and bookmark citations used in the text that the readers wants to look at further. It should be possible to add annotations to all of these.

Problem it solves

 * Registered users "abuse" their watchlists as a bookmarking/read later tool. Their watchlists often get too big because of this.
 * Logged-out users cannot bookmark articles at all. (Browser bookmarks are tedious.)
 * May help to convert readers into editors if they can also see the "recent changes" to articles in their bookmark list.

Details

 * Should also be available to logged-out readers. On bookmarking something they should be strongly encouraged to create an account. But ideally it would also be possible to bookmark stuff without an account (store in HTML local storage, or something).
 * The lists should carry over once a users signs up for an account.
 * These lists should be private, unlike Gather.
 * Maybe people can export their bookmark lists as books, replacing the broken(?) Book Creator (en:Wikipedia:Books). (May run into moderation issues, if this is too prominent of an option).
 * Editors can insert bookmarked citations into articles.