Very interesting. Bookmarks solve a particular problem of finding information that was already visited. A more general problem is a designing a personal knowledge base. There are lot of hints in this page about PKB and some of them can be applied to bookmarking as well

http://www.acuriousmix.com/2014/09/03/designing-a-personal-k...

I created a personal curation system - Hyperbook, http://getbook.co . It arose out of the need to store reference materials while writing my thesis. There seems to be lot of people working on similar ideas, which shows the market need and lack of existing products which address them. I sense there is a great startup/product coming in this space soon.