That's because Pandora only has about a million songs in their catalog, where iTunes has like 30 million. All Pandora has to do, and you better believe they did in order to write an article like this, is classify an unknown artist that sounds like Coldplay into the system. If you've experienced Pandora, you know that after a few weeks you hear the same music over and over on any given channel. Suffice it to say, across millions of artists and hundreds of genres, one relatively unknown artist with a lot in common with a massive artist is going to be played for a shit load of people a fuck load of times.

If you divide total Pandora royalties by the number of artists in the catalog, you'll realize that these "unknown" artists they're showcasing are outliers by a huge margin, and probably put into rotation just for a publicity purpose like this.

edit: spelling