I guess I was not clear - what I do in the bookmarks manager is go into a folder, and select and open them in groups of 20 or so, then delete them as bookmarks. So bookmarks are sort of like "tab cold storage" for me. So for me tagging them would be wasted work since they will eventually be deleted regardless. I also do use bookmarks for the awesomebar but it is mainly so they are prioritized in normal autocomplete.