I'm not convinced by what people say. It might be partially true, but i think there's something deeper behind it: blogs, music and video are addictive for the right people. Hence they'll spend a bit of effort to ask around what app to use, and ask about good tv, etc. Also because they're addictive and the barrier for sharing is much lower, they'll get shared much more often, talked about much more often - so you get discovery.

Podcasts aren't addictive(and i like podcasts). Lectures are boring by nature, and demand tons of focus(something we we may have more than the average guy). And even in fields that could be addictive(and don't demand great focus), like comedy, the quality is terrible - most comedy podcasts don't even come close to professional comedians doing standup.

Here's one idea: build a podcasts comedy site that curates only consistently great podcasts, and enables extremely easy sharing including sharing of very short segments.

Make the transition from the using the site to using it while driving easy and habit forming.

I think doing that you can get users "addicted". And once they are, they'll get your app, they might listen to other podcasts, etc.