We recently asked our SEO director, Adam Hankey, Does Google Give Mobile Sites More Credit?  Here's his expert answer we'd like to share with all of you:

"Regarding the question, Google does indeed change the results a bit for those searching from a mobile device.

In the actual words from Scott Huffman, Google's Search Quality engineering director, "One of Google’s tenets is that we want to let you search the whole web, and in the mobile world the whole web is more than just the whole web that we normally think of. There’s another web, if you like, that we call the mobile web. And all I mean by the mobile web is sites and pages that are really optimized and made for mobile devices, right? Things you probably don’t want to return very prominently on the desktop but they’re very important results in mobile search. In the US you get things like CNN and other prominent sites where what they’ve done is taken their, typically taken their desktop site and made a nice mobile rendering of it for mobile users. "

Based on all of that, I would say you do get some added advantage in the algorithms if your site has mobile device formats.

Google wants to present what is going to satisfy the user the best, so you have to make available to them what they are looking for in the format that will work the best on their device.

Hope this helps,
Adam"