According to Pingdom's coverage on StatCounter's collection of data from 3 million websites, Google's market share of mobile search is 98.29%. Possibly even more surprising is that Google's mobile search share is significantly larger than their desktop market share. The red bars are the desktop search market share, while the yellow bars are the mobile search market share.
Pingdom notes that "Google’s piece of the mobile search pie is even larger than their already impressive share of the overall search engine market. For Yahoo and Bing, the situation is the opposite. Their mobile efforts are nothing compared to their search engine market share."
AndroidGuys gives their advice to AT&T regarding Google Search:
Our advice to AT&T is this: Go ahead and load Yahoo! and Bing onto your devices. Giving users choice is awesome and we applaud that. Just don't be surprised when customers continue choosing Google.
Pingdom mentions that the data points to a very successful Google:
Google seems to have taken the necessary steps to bring its search market dominance over to the mobile sector. This much thanks to its early collaboration with Apple and later secured by Android, which ironically now is the very thing that threatens Google’s dominance since it has made Apple a rival.
Thinking back to last year, AndroidGuys notes that "Google's mobile search share was at 95.58 percent. Where will we be this time next year?"
MobileCrunch points out that Yahoo accounts for only 0.8%, while Bing and other search engines tie with half of Yahoo's figures.
Image from Pingdom