Sorry... a friendly disagreement. First I never came across a song written to vox populi. Most songs were written by one person. If it reflected the views and life of those around them, and they could find something in it to enjoy, then the song took on a life of its own, which may have gradually been shaped by yonders vox populi and passed into the tradition. Are Woody Guthrie's songs not folk songs, because he wrote them? If songs are written out of love and living of a tradition, they may well become folk songs. I think it all boils down to the old question... are your roots showing?