Pandora released its latest monthly listener report and investors did not like its tune. Listener hours increased 28% to 1.73 billion in May versus last year's 1.35 billion. Pandora's share of U.S. radio listening reached 9.13% and active listeners reached 77 million, both better than last year. However, the stock is dropping almost 5% this morning because bears are worried that Pandora's radio share dropped from 9.28% in April to 9.13% in May, and that listening hours and active listeners are flat. For the past year Pandora's stock is up 44% but has slid 7.48% YTD. Investors are also worried about the Apple/Beats deal and that iTunes Radio may finally start to steal market share from Pandora. Pandora says May's report will be its last monthly metrics release and going forward it will only release listener data quarterly. Debra Borchardt reports from New York.