www is deprecated
According to this site www. is deprecated. They are trying to persuade people to use
site.com instead of
www.site.com. The site defines three levels of compliance: Class A your site allows either, Class B your site redirects all www requests, and Class C your site does not define the www subdomain.
I wouldn't go making your site's Class C anytime soon though (they have 59 sites listed that have done so already, though the site is Class B!). How many clients do you have that can't access their web mail because they type
www.mail.domain.com instead of
www is almost implicit nowadays - not going anywhere.