Think digital coupons. That’s one interesting suggestion that emerged from the Public Radio Development & Marketing Conference in San Diego. Blogging the confab is Keith York, a KPBS programmer who writes the Public Media Digest. York reports that Paul Jacobs of Jacobs Media told a packed session that use of digital coupons is surpassing printed coupons, so stations could offer listeners online coupons and discounts for sponsors. A leader in digital coupons, Safeway, added them to its loyalty card effort last month, the database marketing blog DM News reported. Forbes said some digital coupons fail to offer meaningful savings and even charge memberships to prospective users.