Measuring the return on podcasting investment

I met with a prospect this morning, trying to convince him that he needed to add podcasting to his online marketing mix. While he was intrigued, he questioned the ROI. In particular, he wanted to know how one can measure the podcasting results.

Okay, I can understand why one would want to measure podcasts. But my goodness, why is it that people put so much pressure on internet marketing tools? No one would go to television network and say, "For my 30-second ad, how many actual viewers watched it? No, not just the CPM, I mean actual numbers?"

No marketing director can tell me that a person walked into their car dealership or that someone chose one shaving gel over another as a direct result of an ad they viewed on TV or heard on the radio.

I'm not talking about brand awareness. I'm talking about the direct correlation between someone seeing an ad on TV and then going to their grocery store to buy that item off the shelf. Those type of metrics don't exist, not unless you run a specific contest or other campaign.

So, why is podcasting being treated differently?