I also use book giveaways to build big email lists (and get more traffic). (creativindie.com)
The prominent blogs on both sides have large but still niche audiences, just as talk radio hosts, politicians and environmental groups with big email lists do. (epolitics.com)
I believe them, but I honestly don't have a very big email list yet, so I can't speak through much experience. (stephaniecainonline.com)