Why the US has so many drug commercials on television

An interesting video from Vox about why prescription drugs are so prevalent on US television and how they can easily be argued to be both good and bad for public health. I guess it's safer to say that the direct-to-consumer prescription drug business is really one that relies on fear of something that may not exist at all. You know, sort of like when you look up symptoms on WebMD (don't do it).