Here’s some fuel for mobile advertising: Nearly 77 million U.S. mobile subscribers recalled seeing some form of advertising on their cell phones — an 81% increase from a year ago, according to a new study by Nielsen Mobile (per MediaPost). Still, advertising has lagged behind the growth in mobile media usage; 63% of mobile ad viewers see ads just once a month or less. What’s more, less than two-thirds of page views of top mobile sites carry advertising, and half of that inventory is taken up by unpaid house ads.

