They need to add another feature. At the present time you can't a real domain name point to the dot-mac website.
Apple needs to work a deal with GoDaddy.com or one of the other domain registrars to bundle domain registration with a dot mac account.
That way you can use your dot mac account for your church website, club website, small business website, etc.
- Dan Ashley
What's Wrong With .Mac and How to Fix It