Last year google released an article on their developers blog for webmasters regarding smartphone websites. This article explains a few options you have when designing a website to be mobile optimized. It also gives Google's offical recomendation on the matter. The article states clearly:

Google recommends webmasters follow the best industrial practice of using responsive web design, namely serving the same HTML for all devices and using only CSS media queries to decide the rendering on each device.

- Building Mobile-Optimized Websites

Google co-founder and CEO Larry Page expressed frustration with websites specifically designed for mobile devices.

We don't necessarily want [our advertisers] to have mobile sites… I find I get frustrated on my phone when I hit these mobile sites… I just find it confusing… As an industry, we need to improve these experiences… I’d almost say that we shouldn’t be designing for mobile. The kind of mobile phones we have now, the state of the art, are a little bit beyond, and those experiences [i.e., full websites] should work on those devices as well. I'd like to see us move in that direction.

- Google co-founder and CEO Larry Page