Google has acquired a leading firm in mobile advertising, causing observers to think that mobile advertising will take off in a big way. The growing popularity of the iPhone and other powerful mobile devices ensures that mobile ads will become more ubiquitous, but predictions for the growth of the business vary widely. “We see mobile as a huge growth opportunity for us,” Susan Wojcicki, vice president for product management at Google, said in an interview. “We see an opportunity working with AdMob to really accelerate our efforts in an important industry for Google.” Google is already ahead of its rivals, Microsoft and Yahoo, in one segment of the mobile advertising business: ads linked to search queries.