Before today you would register your .CA domain name then be asked for information which would be displayed in the whois information. CIRA the authority on .CA (Canadian) domain names has changed there policy so having the information displayed in the whois is optional.
Prior to this policy change, through a simple WHOIS command, anyone could get extensive details on the identity of any Canadian who personally registered a .ca website. For example, say you were a Canadian guy who had a great love for frying pans, and you registered the website www.fryinpans.ca. You’d be required to submit your personal information in order to register the site, and than anyone WHOIS’d www.fryinpans.ca would learn your home address, personal phone and fax number, full name, and personal email address. Needless to say, the easy access to this much personal information is open to abuse. Identity theft and spam come to mind.