Duplicate Content and Search Engines
I was ironing out some permission problems with a WordPress install the other day when I learned a little more about the .htaccess file.
If search engines find both www and non-www links from other sites to your site, they may treat https://YourSite.com and https://www.YourSite.com as two different websites with the same content. Trevor Ginn from Trevor Ginn advised me a while back that a site could be penalised for duplicate content.