Yahoo! previously told me that one of the reasons the company wasn't aggressively pushing search advertisers into mobile as Google is doing is because most of these ads aren't optimized for mobile, including landing pages, and thus would not offer a good experience for advertisers or users. To address this issue, the Inside AdWords blog is promoting the creation of mobile landing pages using a wizard Google has set up:
AdWords Business Pages for mobile ads
Mobile ads can refer users to a business phone number, a mobile website, or both. Usually you need to be a web developer or contact your webmaster in order to create a mobile web page from scratch. However, AdWords Business Pages for mobile ads provides a friendly wizard that creates a page for you in minutes - which is available immediately after you create it. Google hosts the page for free.
We've just expanded carrier targeting in more countries, which means you have more options to fine-tune who sees your mobile ads. Click "Advanced targeting and network options" to expand your options for carrier targeting from the "Create/Edit mobile ad" page. You can choose to show your ads to users on all mobile carriers, or check off the boxes next to the specific carriers you want to target.