Pit podcasting against traditional broadcast radio in the time-sensitive content genres (politics, business, news, sports) and podcasting loses. Now, broadcast radio has its problems (fodder for another post or three), but it continues to have massive reach. Radio mostly retains its popularity because it is timely -- a constant source of fresh information.
Timeliness (particularly in terms of the mobile device) is podcasting's biggest weakness. If you can't propagate your media to your end user's device in a timely manner, the vast majority of current content loses its punch. It is literally yesterday's news.
A podcast has a long and tortured journey from creator through aggregator (like iTunes) to local computer client, where it waits for the user to plug in their iPod and synch it. Even then, once the programming is on the iPod, the user has no idea if they've got new programming unless they actively go and look for it. This channel does not lend itself to effortless, immediate consumption of time-sensitive programming.
The phone is by its very nature a connected device. FoneShow gives its users instant notification of the availability of new programming, and a channel to consume it on -- as soon as it's published.