Assisted stretching, done in a therapeutic manner, has many advantages over traditional stretching. A lot of it has to do with the ability to isolate the muscles in various ways that is very difficult to do by oneself. In assisted stretching we have the ability to work not only muscle groups, but individual muscles within those groups, we can stretch them in their insertion or origin points, we can strtech the fibers in various planes making sure we target taut bands that are impeding proper function within the muscles.
Assisted stretching is a very powerful tool whether you are an athlete and you want to improve your performance, spend a lot of time in front of a computer and want to undo all the tightness that sitting does to you or you want to take your yoga practice to the next level.
Assisted stretching is for every-body, and is little by little is becoming more popular. Here is a New York Times article that talks about this.
Stretch Therapy and Bodywork 