I personally have 10, but one is disabled. The extensions that I do use are –
Fasterfox (only a couple of tweaks, and I love the page load timer)
Digger (which lets you go up the directory structure of a website quickly with a right-click on the Go button)
The disabled extension is Popup ALT Attribute. I don’t mind that there are a lot of graphics that don’t show a tooltip – as it is most sites are now using the title attribute to tell you about images and other things.
So anyway, the point of the Lifehacker piece was that this person had installed 200 extensions at one time. I personally don’t have any need for more than the ten that I already have.
Incidentially, there’s even an extension to tell you what extensions you have. I guess that this would be for the person who just says install at every opportunity to install something. There’s also a thread about this at the CyberNotes site. It seems most of the people posting in that thread are firm believers in more is better. Ah well – nothing I can do 🙂