Accustream iMedia Research pointed to a 26.1 percent increase in total listening hours in 2007 to 4.85 billion. That is drawing more advertiser interest, though the group credited heavyweights Clear Channel and Citadel Broadcasting for drawing the most advertising visibility. In total, internet radio billings topped $80 million in 2007, according to the group, almost triple sales of $26.9 million in 2006. (Digital Music News)