iamlost - 6:15 pm on Feb 22, 2011 (gmt 0)
I have become a believer in the Luke Wroblewski approach of designing 'up' from the mobile version.
It is an interesting approach starting with the greatest constraints and then loosening as possible. It also ensures the least problems: in display, in load time, in ease of use, in function, etc.
As small mobile screens are now outselling larger desktop screens designing for mobile is increasingly designing for the customer. Granted, a mobile first redesign is not something to be undertaken lightly; however, for new sites it is, in my mind, now best practice.
I agree with pageoneresults:
The goal is to keep your content all under one roof. No need to start another site just for mobile if you can use a separate stylesheet served based on the UA. I'd like to think you don't want to fragment the content. People will visit and bookmark the same pages from your site when using a stylesheet to serve mobile content. Things will be a little different if they are visiting and bookmarking m.example.com or example.com/m/. Remember - One Funnel
CSS3 Media Queries are a webdev's new best friend for cross-device site building.