Protest, resistance and rebel songs are a major aspect of folk music, so it's no surprise that someone should apply that ancient tradition to the Occupy Wall Street movement. I have no idea who Bill Allyn is except that he's the author of the song “Expect Us!” and he encourages people to share it as widely as possible.
As rebel ballads go, I've definitely heard both worse and better. The lyrics are pretty basic, but the way he presents them is emotionally effective. The version of it I found is paired with dozens of photos from the worldwide Occupy/15M movement, some of which are quite inspiring. One of my favorites shows a police officer (from England, maybe?) holding a sign that says “I've chosen the side of the people.”
This may not go down in history as one of the all-time great protest songs, but I imagine it would be a powerful experience to sing it in the company of hundreds of other Occupiers in a plaza somewhere at night. Thanks to Bill Allyn for putting the hopes and dreams of Occupiers all over the world into a traditional protest ballad. I know a number of other musicians have made Occupy music of various genres, but most of their songs are hip hop or some other “modern” form of music. I think this one is the most “folky” example I've found so far. Maybe some other folk musicians will follow this example and add to the Occupy folk music repertoire.