The largest offender has been Internet Explorer 6. Its market share is waning. Serious updates are being force-pushed to help old users. Internet Explorer 8 (beta?) will probably be out before the end of the year.
As I start working on my next book I have to ask questions like this. If I write about memory leaks will it even matter by the time the book is published? (Not saying that the book won’t happen until 2009, but that’s probably when it’ll be on most bookshelves.) Memory management will always be an issue, but memory leaks (as we know them) are surely doomed – it’s just the time frame that is unclear. Regardless, I think there should probably be a web-only article on memory leaks, I’m just not convinced that it should be in the book, proper.