Using Image blur to add impact to your action shots is a good way to give your images a sense of motion and life.
When taking shots of fast moving subjects such as sports or speeding cars on the road most photographers prefer to freeze the action to give a clear view of what is going on. However there may be occasions where the adding of blur will actually enhance the image and help to illustrate what is going on better.
For instance if you want to create an image that shows the hustle and bustle of busy people on the streets or perhaps speeding cycles in a street rally, then adding blur or should I say keeping blur will help to illustrate this.
This Video from DLSRTIPS.COM shows you how to achieve selective blur in your photography.