I know a couple of people that like to open lots of tabs and also swear by Tree Tab. I haven't used it personally because I rarely have more than half a dozen tabs open at a time.

Tree tab is a must for me when doing research. This morning I closed a few Firefox windows. The largest had 421 tabs, the others around 150-200 each. I might be a compulsive middle-mouse-button and new-tab user.