The band The Black Keys recently settled its lawsuits against Pizza Hut and The Home Depot, which the band alleges were using The Black Key's songs in advertisements without paying for them. As you can guess, if that were true, it would be a merchandising and licensing issue.
With their duet "Good Time," Carly Rae Jepsen and Owl City have a hit on their hands.
Generally, a work has to be very similar to another copyrighted work in order to be considered infringing on that work's copyright. But here in Los Angeles, where it can seem like everyone is working in different versions of the same idea, it isn't easy to understand the contours of copyright law.