How Do You Know a Story is Worthy of a Podcast Series?

I wish I had a nickel for every time someone says, "I think that
story would make a great podcast series." In my head I usually
think, "Nope. Wouldn't work." But why? How do you know you have a
story worthy of a podcast series? Emily Guerin of Southern
California’s KPCC has a few answers. She produced a
five-and-a-half-minute feature and turned it into a 9-part series
called "California City: The Dark Side of the American Dream."