Actually Cas, the hosts are being helpful.
The vast majority of users are not that experienced and assume that the "www." is part of the domain name.
That's why I strip out the "www." from the client login form on my webdev site when it's submitted.
Try pressing "login" on the link below and see what it changes to:
http://clients.phpfuture.net/?user=www.cableforum.co.uk