For example, if you do a whois lookup on About.com, you'll find that they are based in New York, with a phone number of (212) 204-4000 and an email address of firstname.lastname@example.org. You can also find their mailing address there.
Many people are uncomfortable with that level of exposure, and so domain registrars offer privacy protection, usually for a yearly fee. Do you set up privacy protection on your domains? Why or why not?