I have to disagree. In my case, bookmarks are the place where "tabs" go to die. I use Tree Style Tab addon, and tabs (mostly self-)organize as I surf, do research on different topics and whatnot, and I jump in with a window title changing addon or grouping parent tab. I cannot even imagine using a browser without it. But bookmarks do not preserve any of that relational data. Session managers are also luckluster solution at best, because merging a few tabs, a tree or window with existing session is clunky at best. After many years of frustration, I have started working on my own tab syncher/organizer.

Bookmarks are only the coldest of storage for me, with exception of bookmarks bar where I place often accessed web sites.