Think about the kind of data that they would collect. I personally rarely use Shazam, but when I do, it's more often then not a song I don't know at all rather

Think about the kind of data that they would collect. I personally rarely use Shazam, but when I do, it's more often then not a song I don't know at all rather than trying to remember a song's name. So someone like me hears a song and wants to identify it. Then another person, and another. So you have three people in a specific location at the same time looking to identify a song. That would suggest that those people like what they hear. You know what the song is so you know interest has piqued. If you cross reference that with radio plays at that time you have a new metric that you couldn't measure previously - reaction to a radio play. It's incredibly interesting because of the type of data it collects, which to be honest I think the article explains explicitly and very clearly!