I was very dissapointed to see http://news.bbc.co.uk start to redirect to http://www.bbc.co.uk/news/ earlier this year.

Besides the longer URL with the deprecated www. prefix, hosting Web applications on paths is dumb. Why?

There are several practical reasons why hosting by domain is better.

It forces developers to think exclusively for one particular application. So one can focus on designing URLs for it, without worrying some other URL dispatcher getting in the way.

The site is just an A record if you want to transfer the application to another host. You can’t do this with paths sanely.

It is usually much easier to setup a local running application with VirtualDocumentRoot and a simple change in /etc/hosts, if it’s designed to sit on a domain.

It’s easier to scale with domains hosted by domain. With an application hosted on an domain it’s straight forward to start mirroring it and utilising geoDNS.

It’s a more resilient model. Again by using DNS you can configure backup hosts running your application.