Podcasting grew for years without a .
Anyone could publish a , and any app could play it.
That openness produced an unusual range of subjects and voices.
It also made the medium hard to measure, which limited advertising .
Platforms then offered large sums for shows.
Listeners disliked being moved, and several expensive deals underperformed.
The industry has since settled into a mixed model.
Shows stay open, while extra episodes and no advertisements sit behind a .
Audiences are small by broadcast standards but unusually .
An advertiser reaches a listener who is alone, commuting and rarely skipping.
That attention, not the audience size, is what is actually being sold.
The risk is the same one that changed other media.
Once attention is measured precisely, it tends to be filled more densely.