In this video Leo Laporte (who is set to make about 6 million this year with his podcast) talks about why people should start a podcast.
All you need is a passion.
The cool thing about podcasting is its niche. Unlike radio which is broadcasting, podcasting is narrowcasting.
He also says you can't make money with a podcast, I disagree. You may not quit your day job, but you can make money with a podcast.