There is another thread about it here

http://www.flyertalk.com/forum/trave...-even-had.html

Most of the media is missing out that for 99.5% of the people applying for a passport every year (about 14 million), they will be able to prove their citizenship and not need to fill out this form. They expect only 75,000 people to actually need to use this form.

If for example you have a passport already, that proves your citizenship, and you won't need to do this form. If you can produce a birth certificate, that proves your citizenship and you won't need to do this form.