If you go to cira.ca and search for a .ca domain, there is a new message at the top of the page. There will be a change to the .ca WHOIS policy starting June 10.
As of June 10, 2008 the dot-ca (.ca) WHOIS will not release information about individual Registrants and their Administrative and Technical Contacts. The personal information of corporate Registrants will be displayed by default.
I'll have to check after June 10 to see what this means, but it looks like you won't be able to see who the owner of a domain is, unless they're a corporate Registrant.
This could create a problem if there is a .ca domain you want to buy, but you have no way of finding out who owns it. It would also cut down on unwanted emails, if you have lots of people contacting you about domains you don't want to sell.