And then, there's what's known as a "NaNo Rebel," which is now allowed for on the official site. It means you're participating in the fun and support, but on your own terms, writing something other than a 50,000 word novel draft.
That's what I am this year. I'll be working on a non-fiction book that I have all kinds of notes for, and it will probably be less than 50,000 words.
See ya on the NaNo site. Be there or be square!