Anita Campbell has a very interesting post on pay per call advertising. I have never heard of this type of product before, but it definitely seems like something worthwhile to explore for small businesses (and businesses in general for that matter). This kind of product seems like it would help to eliminate click-through abuse as well as set the bar a little higher on screening customer prospects in certain biz models.
Professor of Practice of Behavioral Economics | Academic Director of CEMS Master in International Management (MIM) Program @Cornell