A new survey of U.S. adults found about one-quarter have used location-based mobile services. The Mobile Marketing Association survey, conducted in partnership with Luth Research, also found that mobile users are more likely to respond to mobile advertising delivered with location-based targeting than regular ads. Overall, 91% of American adults own a cell phone, the survey found. Within this group, 26% (23.7% of the total survey group) have used a map, navigation tool or some other mobile service that determines their location. While 10% of cell phone owners (9.1% of the total) use a mobile location-based service at least once a week, the number is much higher for iPhone owners: 63%. In terms of age cohorts, adults ages 25-34 were the heaviest users of location-based services, with 22% doing so weekly. Most respondents said that they used location-based services to locate nearby "points of interest, shops, or services." What's more, roughly half of those who noticed ads during their use of a location-based mobile service took some kind of action. That's substantially more than the 37% who took action while sending or receiving text messages and the 28% who did so while browsing the mobile Web. Separately, a new report from Borrell Associates titled "Local Mobile Advertising & Promotions Forecast" predicts that mobile marketing will enjoy explosive growth over the next four years, driven largely by local mobile coupons. Borrell sees mobile coupons growing from $2.7 billion in 2009 to $57 billion in 2014, for a cumulative annualized growth rate of 84% per year. Mobile advertising will grow from a $285 million business in 2009 to $11.3 billion by 2014 -- increasing from about one-tenth of total mobile spending to about one-fifth. The Mobile Marketing Association surveyed more than 1,000 American adults.