During my daily browsing sessions with Firefox I tend to open more tabs than the browser can actually show on its interface, so I end up with half-displayed titles and a horizontal scroll bar that makes navigation really awkward.
That's why I love this extension I just installed. FaviconizeTab reduces tabs to the minimum possible size: the favicon. As each tab takes only a few pixels, you can open many more in just about the same space. Then you only need to be able to associate each favicon with its correspondent website.
The only problem I see is that if you open more than one page belonging to the same website, you'll get the same favicon. But then again, it's just a question of memory.