Thanks to spammers, making your email address visible on the web can be a painful mistake. Spammers, of course, often harvest email addresses using automated programs, and when doing so, they pick off the lowest hanging fruit.
One particularly tasty piece of fruit: the WHOIS database that provides access to domain registration information.
In response, many domain name registrars offer private domain registrations. With a private registration, the registrar’s contact information is displayed instead of yours, leaving it harder for spammers (and shady direct marketers) to use WHOIS for nefarious purposes.