Okay, I confess that I might have some tabby issue. I wrote Keep Last Two Tabs extension for Chrome to prevent accidental quit.

I think it has been a long time, I always have to manually create a tab beside the pinned tabs in Firefox. Somehow, I can feel comfortable without an unpinned tab. It has to be look like

There must be one unpinned tab! (Any good shrink? xD)

Actually, it makes sense since you don't want to change URL of pinned tab, that's why you pin it at first place, isn't it? As a Pentadactyl user, I can always your keybinding for new tab, so I will open URL in new tab directly.

But every time when I look at the tabs bar, it just doesn't feel right without an unpinned tab.

So, I added few code to my configuration of Pentadactyl. I need to implement in Firefox, not on top of Pentadactyl by using autocmd, which does not have tab removal event. However, you can check tabs with LocationChange, but that will have many unnecessary checks.

Note that closing animation will cause tab still remains for a short time after TabClose event is fired, but it can be checked as you can see in my code. The code also takes care when open tab just gets pinned by attaching to TabPinned, it will immediately create a new tab.

I think the code could be used directly in Vimperator as well.

I am glad Chromium is not my main browser, or I will also need to add new option to KLTT for similar thing.