Honestly think stuff like this will replace the magic quadrant type of stuff that research/analyst firms focus on now.
Identify the key players like this, then one that shows their development over time (so, for podcasting, we'd see Dave Winer, Adam Curry through to the new enterprise stuff a la Serial), then the same identifies the stack of technologies and how they intersect, (libsyn through feedburner), and, where this could go.
Anyway, cool to see @danbenjamin on here.
Like it, thought it's more a mapping of the "nerd culture" podcast universe. Light or missing significant chunks/genres like comedy (I couldn't find Earwolf - maybe I missed - but that's a massive exclusion if not included). Also whole worlds of podcasts around food, auto, celebrity (Podcast One), etc.
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There's a few, popular, original podcasters missing here.
Pop Rocks And Home Brew: A Family Tale
developer tea
VC Puzzle
The State of Snapchat Analytics