Mark wants to do a podcast and his partners say Podomatic is great because it's free. But he's thinking of going with WordPress and their podpress plugin. Leo says that either would work. The difference is that doing it on his site will mean he absorbs the bandwidth costs. Podomatic uses ads inserted into the site to cover bandwidth costs and profit. But they handle the burden of scaling it up if his podcast gets very popular.
Mark will also want to create an RSS feed so that his audience can use pod catcher software to find it every week. He should worry first about building his audience. Until he has thousands of listeners, he won't have an advertiser interest. Once he does, then the agencies buying podcasts will find him.