Jane Ruffino: Goal for podcast sponsors is to reach a motivated, niche audience

I’m writing this wearing my Mailchimp t-shirt. Its customer service team sent it to me a few years ago following a helpdesk chat where I was apparently pretty entertaining in my newsletter software mini-crisis. A few months later, that t-shirt became hot property, thanks to Serial, a true-crime podcast that was spun off from long-running storytelling programme This American Life.

Serial created the world’s first podcast celebrity, in its producer and presenter Sarah ...