Is GMail for domains the next from the goodies bag? Reasonable speculation I think.
Assuming a new feature for domains is in the making, this is how I see it working. After deciding to use GMail as a mail server, the first step would be to add an MX record pointing to mail.google.com in the DNS for a domain — effectively routing email directly to Google for it. GMail will not automatically put this incoming mail into your inbox as there is no link between that domain and yourself.
In your settings, there will be a tab to manage your domains — giving you the ability to link domain(s) to your account. I would guess an authorization email is sent to the administrative or technical contact before it's officially added to prevent random people from adding domains they don't own.
Once a domain is linked, you can then manage email addresses for it by clicking the "Manage this domain" link (as seen in the javascript) when you are logged in as the administrator. It is likely that the domain email administrator could even set up quotas to best manage the 2GB of space given to them — unless they are willing to pay for extra of course.
