I have tons of tabs open, because bookmarks suck. EG if I'm working on a project with a new framework I might need to reference 3-4 APIs, and 5 classes in each, and 2-3 methods per class in a given hour or two. I want a tab for each method, with a tree of the parent classes and APIs. Tree-Style tabs lets me have that, but Firefox's bookmarks don't. So I leave tabs open. That results in 50-60 tabs or so. Sure, I close the tab group when the project is done, and subsets when I'm done with them, and use different windows to separate different projects/activities, but it results in lots of tabs. "Normal" people use tabs for current pages, I like to have both the current pages and a herarchical history of how I got to those pages. I also open all links in tabs. Tab hierarchies provide a combined history (with list of what lead where,) bookmarks, and tabs, all in one convenient interface. If bookmarks supported this nicely it would be great, but they don't.