Whois privacy protection is simply a means of masking your details with that of your registrar, there are many reasons for this (spam, junk mail, prank call etc) however it does not provide you full anonymity in respect to any legal action. As your registrar will be forced legally to provide your details to the various authorities or legal firms/teams for various reasons.
Whois privacy is also fairly futile if you apply it after you have had the domain "un-protected" for a long period or are planning to disable the protection for a transfer, the reason being the details would have and will be cached already around the net on various search engines and whois lookup sites.
hope that helps :thumbup: