Do not package those that are well maintained

I know that it might help distribute only compatible versions of firefox if their is an ubuntu package. But I don't think any future versions have a big risk of being incompatible.

I think ubuntu should de-couple itself from firefox, and let firefox update itself, since it already has a very good mechanism to do that. Since security fixes, etc. come out very fast by firefox directly.

This may also be something to consider with other well maintained packages that publish thier own updates...