If Spotify gains enough market share then it will effectively become the de facto gatekeeper of podcasts (similar to how Google Play is the de facto gatekeeper of Android apps despite side loading and alternative app stores). Once that happens many of the benefits of podcasts will be destroyed. Creators will no longer have full creative freedom as ... See more
If Spotify chooses to continue on their current path of exclusive content it will break interoperability with other podcast apps and force listeners of those shows to use the Spotify podcast client. I suspect that many listeners will also transfer their existing subscriptions into Spotify to avoid needing two separate podcast clients.