Pandora is courting ad dollars by suggesting that its audience can be better specified than regular radio when determining the listener's age, sex, ZIP code or musical taste. The still unprofitable Internet music streaming service has seen revenue, largely based on advertising, grow in the past two years from $55 million to $274 million and its registered listeners swell to 125 million. Using its audience segmentation to entice local advertisers is seen as a key to a profitable future.