Pandora was launched about 3 years ago already - in the fall of 2006, practically everybody over here was listening to it. It set the standard for music discovery back then. So by the pace of the internet, it's an app from the stone age now
About 2 years ago, unfortunately, they had to close the service down for non-U.S. citizens because they couldn't get the music rights outside the U.S. Despite the fact that outside the U.S. you could still enjoy Pandora if you faked your IP address, Pandora has lost most of its foreign users to a similar, European-based service called last.fm these days.
But apparently, it's still finding new users in the US of A

Indeed it's a great service - though I wonder how they're still alive after all these years with limited reach and constant rights struggles...