Mobile search could grow from 9 percent of all queries this year to 20 percent by 2012, estimates RBC analyst Ross Sandler in a new report issued today. There is still a huge gap between mobile's share of overall search queries and its share of search advertising. Sandler estimates that mobile will still represent less than 2 percent of search ad budgets this year, compared to the 9 percent overall share. But he thinks that gap can narrow and that mobile search advertising can be a $2 billion to $3 billion market in 2012. His assumptions seem a bit aggressive on the ad revenue side. There might always be a gap between mobile search share and mobile search ad spending because of the relative effectiveness of search ads on PCs versus on mobile phones. But Sandler does a deep dive into mobile search advertising and comes up with some compelling reasons why that gap should at the very least begin to narrow just as mobile search starts to take off thanks to the growth of large touchscreen devices such as the iPhone, iPad, Android, and Blackberry.