API or Implementation?
Ted Tso has written an in-depth blog entry about the recent “ext4″ defect which he (and many other people) see as defects in the user software, not the kernel.
The core of the issue is applications that have been coded to an implementation, not to the API. This is an issue that hs been discussed a few times on Raymond Chen’s Windows blog, and has no easy solution. The kernel developers are wont to completely ignore backwards compatibility though, so I suspect the most popular “broken” software will be fixed pretty quickly.