>>10
It could also be said the Gecko was pretty badly coded to begin with, but I think it's pretty foolish to think they started totally afresh. There was probably a lot of duped code from NS4 even though it was marketed as a total revamp (Opera did this with version 7, but I've no doubt there's loads of pre-7 code in Presto, for instance.)
Also, the "new Netscape" was still built on all sorts of retarded premises and ideas that do nothing for the user, like XUL. The "WE WILL BECOME THE DESKTOP!" mindset of confused-late-90s-Netscape is prevalent in 2006 Firefox in both the source code and Mozilla's attitude to the community. Why else would it be the most bloated and second-most insecure browser, despite being one of the largest and most prominent open source projects ever?