"People will make changes to do something good for Firefox and because Firefox is the only really blessed project by the Mozilla Corporation and the Foundation, that’s their only focus. So they’ll make changes that work great in Firefox and then they’ll do—they’ll either like, break Camino’s build just entirely, or things will stop working, or things will slow down, and nobody will really understand why. Because, you know, there was no communication about, you know, this change might have this effect. There’s also a lot of strife back and forth between features that are implemented in the core Gecko in a way that they will only work with Firefox. [...] So we’d run into situations where we try and implement a feature and we discover we just can’t do it. And we kind of raise our hands and say, “Ah, can we get this fixed?” And the answer would invariably be, “Well, it works in Firefox. Who cares?” [...] And that’s something that eventually made me sour greatly on the Foundation and the Corporation and why we kind of took our ball and went elsewhere, and stopped trying to work directly with the Foundation for the majority of problems."

http://mozillamemory.org/detailview.php?id=7277