Most customers who have a complaint about the service from an airline might call the airline about it. Some might write the company a letter. Some might even go online and write blog posts about their bad service. But this guy decided to put his story of woe to a song.
Update: Looks like United got the message. They just posted a tweet saying “@tinamack This has struck a chord w/ us and we’ve contacted him directly to make it right.” Good for United that they finally responded. But it’s unfortunate that it got to this point first. At the same time, the guitar player should have never checked his guitar in the first place, but carried it onboard with him.