If you don't use firefox and don't know what tabbed browsing is, the above makes no sense. Oh well.
As it turns out, that your 'home page' in Firefox can be a collection of pages in different tabs. This is a feature I guess, but what happens if you go to a new tab window in Firefox and hit the home button? Well it opens new tabs for every page in the list after the first one.
So if you set your home page to be 2 tabs, both pointing to your home page, every time you hit the home button, you get an additional tab. If you open 50 tabs, set your home page(s) to those 50 tabs, then hit 'Home' again, you will have a 100 tabs open.
You could use Firefox a long time without running into this, I reckon, but it sure seems like a browser feature in need of refinement.