In the famous book ,Permission Marketing by Seth Godin ,the difference between the easiest & most common form of marketing i.e. Interruption Marketing and the most desired form of marketing i.e. Permission Marketing stands out.

An interruption marketer is like a hunter who wants to use the power of reach to put across the message to as many customers as possible.

Whereas a Permission marketer cares about frequency and like a farmer crafts his message to nurture the relationship with only those customers who provide the permission to communicate.

Wonderful comparison that brings out this difference in the most apt manner.