I use the Domains By Proxy service, too. I use it because #1 I am female and I don't want stalkers coming around bothering me because they think I'll be an easy lay because I work in porn. This happened to a friend of mine who ran a rather popular link list. THREE separate men found her address by WHOIS and started stalking her. One even tried camping in her back yard with a tent! She finally had to move.
And #2, I do it because I have kids. I don't want to risk even a small chance that they could be harmed by some psycho. I know that there are still ways to find out where someone lives, but why make it easy? And I can't afford to get and office right now. And now that WHOIS information MUST be correct or you might lose your domain, there really is no other option for me anymore.
This is the same reason I don't shoot content. I grew up around photography, my dad was a hobbyist, and I enjoy it. But I don't want to be a 2257 keeper and have my address all over creation.