This sounds like a service that I'd like to use, assuming that it had a strong privacy policy (never share my information with anyone, etc.) and was not financed by ads (I'd pay a yearly fee for it).

Another feature that I think is essential is having an effective way to search through my tens of thousands of bookmarks, including an ability to sort them by age. I'm constantly bookmarking articles which are interesting today, but which I'll have no desire to read in a year (e.g., political stories). In fact, it would be nice to be able to give a bookmark an expiration date when I create it, so I won't have to go back and manually purge all these unread bookmarks that I probably will never get around to reading. (Alternatively, there could be a feature that allows me to delete all bookmarks matching a particular hashtag that are older than a certain date.)