Microsoft and Apple are reportedly discussing the possibility of changing the iPhone’s default search engine from Google to Bing, which experts say could be a significant change in the fast-growing mobile search marketplace.

BusinessWeek quotes anonymous sources as saying that "talks have been under way for weeks," and that Microsoft was a "pawn" in the deepening feud between Apple and Google. The competition has been growing fiercer since Google began competing with Apple in the mobile market with its Android OS and Nexus One smartphone.

Additionally, BusinessWeek says that Google is in danger of suffering financial losses if the rumored move to Bing is made, since AdMob reports that most mobile advertising in the U.S. is viewed on iPhones and iPod Touches. The iPhone is the most popular smartphone in the U.S., so any changes to its default programming are likely to produce measurable shifts in mobile search figures, according to analysts.

ZDNet’s Rachel King expresses some skepticism that the change would mean a great deal to mobile search engine optimization (SEO), but notes that Bing’s app for iPhones is more attractive than Google’s.