Check out this blog post on the Google blog.
Our commitment to accessibility means we strive to provide a good browsing experience for all our users. We faced a stark choice between creating mobile specific websites, or adapting existing sites and new launches to render well on both desktop and mobile. Creating two sites would allow us to better target specific hardware, but maintaining a single shared site preserves a canonical URL, avoiding any complicated redirects, and simplifies the sharing of web addresses. With a mind towards maintainability we leant towards using the same pages for both, and started thinking about how we could fulfill the following guidelines:
Continued at: http://googlewebmastercentral.blogspot.com/
Any thoughts on the blog post?