Guilliaume du Gardier has a pretty good post on the top 10 reasons why existing broadcasters might want to consider podcasting. Some of my favourites in the list are:
A good way to give a second life to a huge amount of content that would directely becomes archives
Generating some rare content, available only and exclusively through the podcast
An interesting way to reach niche audiences that would not normally be reachable for financial means
We've seen a lot of main stream media houses start to offer their wares via podcasts here in North America. It's almost becoming a no-brainer, but there is still a lot of work to be done on the little details. The reasons why an existing media house is considering podcasting are of great importance. If the idea is to just generate traffic and good will, that's not bad. If the idea is to monetize that content, though, many factors come into play.
Monetizing existing content becomes a problem if it's going to be ad-based. Ads have times and geography tried to them and that has to be taken into consideration. Advertisers aren't likely to want to put an add for their summer sale into a podcast that will be downloaded for years to come. Either the manner of advertising has to be limited, or some 'insertion and download time' system has to be put into place. Neither of these processes are rocket science, but it bears thinking about.