If you own a domain, and you have followed the rules, domain registrars store some pretty sensitive information about you, like your home address, your name, your email address, your phone number, etc. This information is collectively called the WHOIS database, after the service/tool that is used to query it for information. Your domain can be taken away from you without notice if they find out you have provided false information to the registrar.
Unfortunately, also because of the rules, this sensitive information is freely available to anyone who requests it, including spammers and identity thieves. There is no effort made to qualify requests for this data, it is simply a matter of someone going to a website and typing in the domain they are interested in.
Which means that if someone wants to stalk you, they know where you live. If someone wants to sign you up for mailing lists and have tons of junk mail delivered to your house, they know where to send it. If someone needs to social engineer their way into your company, they have the name of a guy in your IT department because he's your technical contact on the domain. If some terrorist wants to take you out because (for instance) you've exposed their plot to take down the US power grid, they know where to start looking...
That's bad, and the Electronic Privacy Information Center is lobbying ICANN to change the rules and provide some protection of the sensitive data that is collected about domain owners. ICANN is meeting this week, and one of the topics will be the balance of privacy and accountability of the information in the WHOIS database.
In addition to EPIC's efforts, Verisign, the corporate master of the largest of all registrars, Network Solutions, has come out strongly in favor of privacy protections on the WHOIS database. They have set up a new website called InternetPrivacyAdvocate.org that explains some steps you can take to secure your WHOIS data, and also presents a method to voice an opinion on the whole issue.
I encourage you to visit the InternetPrivacyAdvocate.org site and learn what steps you can take to protect the information exposed by the WHOIS database, and also to make your opinion heard about the need for stricter privacy controls on such sensitive information.