What helps sell a podcast?

As reported last week: Tim Bourquin sold the Endurance Radio podcast he's been producing two years. " The key asset, he said, was this: more than two years' worth of shows, featuring interviews with cyclists, trainers, triatheletes, and racers."

The article points out that the key assets of this podcast were not the show but his relationships and trust with listeners. 

Where are the people who are buiding those kinds of realtionships with readers? And why aren't there more of them? Who do you think fits that mold? I'm cruious to find out.