Advantages
A universal medium. Can be enjoyed at home, at work, and while driving. Most people listen to the radio at one time or another during the day.
Permits you to target your advertising dollars to the market most likely to respond to your offer.
Permits you to create a personality for your business using only sounds and voices.
Free creative help is ususally available.
Rates can generally be negotiated.
Least inflated medium. During the past ten years, radio rates have gone up less than other media.
Disadvantages
Because radio listeners are spread over many stations, to totally saturate your market you have to advertise simultaneously on many stations.
Listeners cannot refer back to your ads to go over important points.
Ads are an interruption to the entertainment. Because of this, radio ads must be repeated to break through the listener's "tune out" factor.
Radio is a background medium. Most listeners are doing something else while listening, which means your ad has to work hard to be listened to and understood.
Advertising costs are based on ratings which are approximations based on diaries kept in a relatively small fraction of a region's homes.