All this NaNoWriMo craziness has made me realize that I'm probably one of ten writers I know who aren't participating. Do I feel left out? A bit. But I made a conscious decision not to participate, and here's why.
NaNo is great for getting you started. 50,000 words in a month is huge. If I didn't already have two WIPs I probably would have done it. But I've got 21,000 words of one written, and almost 15,000 of the other. It's not fair to start NaNo in the middle of a WIP. And it's not fair to my WIPs to shelve them while I start on something completely new.
That said, I have nothing but admiration for those who do NaNo. And I hope to do it next year. I just need to have my WIPs done by then!