www subdomain

Giganews Newsgroups
Subject: www subdomain
Posted by:  j (mung_…@att.net)
Date: Tue, 04 Jun 2013

WWW subdomains

Google recommends, and I see that many major sites are complying, with
not having duplicate content on a subdomain. At least that is my take on it.

So, if you have www.some-domain.com and some-domain.com, traffic on
some-domain.com gets a 301 to www.some-domain.com

Can anyone shed some light on why this is being done?