I'm under the impression that no one (or at least very few people) who have 150+ tabs open at once actually use the tab metaphor, at least by itself. I've seen several people in this thread who discuss a tool for searching tabs. Such a person would seldom click on, or even look at the tabs themselves. They would only interact with tabs through the search system. They have already found a new metaphor. Another common system for dealing with large numbers of tabs is building heirarchies. For example, some people have several browser windows open, each wih several tabs in it. One could limit each window to 15 tabs, and only have 10 browser windows open. Roughly equivalent methods include firefox's tab groups and tab tree. Tab tree in particular stands out as a separate metaphor from tabs. While it maintains the ordered list of favicons & titles used by tabs, it adds a new piece of information to each tab, allowing you to more easily determine the correct tab to switch to.