If you've noticed more closed captioning (CC) logos on TV since January 1, 2006, that's due to an FCC rule that requires almost everything on TV to be closed captioned. This includes music videos. Therefore, many music video programs on broadcast TV (like Music Mix USA in Florida and other nearby states) and cable video stations like FUSE now require that submissions be closed captioned. Other stations, like MTV, have always required that video submissions be closed captioned.
There are some notable exemptions to this new law. Based on my research, the following are not required to closed caption: