Splasho made a very nice experiment with firefox by installing about 100 of the most popular extensions. It’s amazing to see all these extensions installed together on the same machine, and certainly you can imagine the load that it could make. I personaly can’t do such experiment, I prefer keeping installed only the extension I really use. Of course I install new extensions, but usually uninstall them very fastly if I’m not planning to use them. Anyway check this screenshot, how do you see the Superbrowser ? SuperCrowded yes ?
http://firefox.phpmagazine.net/upload/2006/03/superbrowser-thumb.png