There is an official Pandora app for Windows Phone, but before that came out, we relied on third party applications like MetroRadio.  Metro Pandora, the SDK that third party applications have relied on has just been pulled due to infringement notice from Pandora.  The complaint will go undisputed. 

Pandora’s DMCA Notice mentions the unauthorized use of their registered trademarks and API.  We can’t blame Pandora for protecting their property.