On Pavlov.net talking about some improvements in memory handling on Firefox 3
It isn’t reasonable to expect all those authors to write code to manually break the cycles themselves.
This reminded me immediately of an MSDN article that took a decidedly different stance
on pretty much the same problem in Internet Explorer:
The good news is that memory leak patterns can be easily spotted if you know what to look for.
and we have no intentions on fixing this any time soon."
Then look at the audiences that these two very different standpoints are aimed at. The Mozilla post is about extension developers, a relatively small and advanced group compared to the number of web developers - the ones most likely to understand the issue if anyone does. The MSDN post talks to "every web developer" and says to "Use defensive coding practices and assume that you'll need to clean up all your own memory." While this may be practical advice for advanced coders, in this context it says to me that there's no intention from Microsoft to really fix this problem.
Kudos to Mozilla for working to improve efficiency and close leaks instead of blaming web developers.