Switching from domain.com to www.domain.com

The recent years I tried to shorten URLs and domains of my hosted websites as good as possible. I did not like using www., why should I add something to make the URL longer than necessary? Even some big websites use no www. prefix, why should my site?
Today this post by yes-www.org caught my attention.

The following points should make you prefer the www. prefix over the 'naked domain':

• Cookies created for example.com are sent to all subdomains of example.com, whereas a cookie from www.example.com is only sent to www.example.com. This means less traffic, as fewer cookies are exchanged (if you use a subdomain for static content for example).
• A second level domain like example.com cannot be used as a CNAME. That happens, if you use an external server (like a content delivery network) behind your main URL (instead of an IP). This will not be possible, as a domain like example.com also needs DNS records like NS and MX.

For me the cookie argument was enough. I was not aware of the send-all, but now it makes sense, why they are so often created for .example.com.