Why Debian GNU/NetBSD?

NetBSD runs on hardware unsupported by Linux. Porting Debian to the NetBSD kernel increases the number of platforms that can run a Debian-based operating system.
The Debian GNU/Hurd project demonstrates that Debian is not tied to one specific kernel. However, the Hurd kernel is still relatively immature - a Debian GNU/NetBSD system would be usable at a production level.
Lessons learned from the porting of Debian to NetBSD can be used in porting Debian to other kernels (such as those of FreeBSD and OpenBSD).
In contrast to projects like Fink or Debian GNU/w32, Debian GNU/NetBSD does not exist in order to provide extra software or a Unix-style environment to an existing OS (the *BSD ports trees are already comprehensive, and they unarguably provide a Unix-style environment). Instead, a user or administrator used to a more traditional Debian system should feel comfortable with a Debian GNU/NetBSD system immediately and competent in a relatively short period of time.
Not everybody likes the *BSD ports tree or the *BSD userland (this is a personal preference thing, rather than any sort of comment on quality). Linux distributions have been produced which provide *BSD style ports or a *BSD style userland for those who like the BSD user environment but also wish to use the Linux kernel - Debian GNU/NetBSD is the logical reverse of this, allowing people who like the GNU userland or a Linux-style packaging system to use the NetBSD kernel.
Because we can.