While this article deals mostly with the line in email marketing, Jessica Sabor's points are applicable to podcasting as well.
"The level of email really depends on the business model," says David Daniels, vice president at Jupiter Research. "Do people really want to hear every day from their airline carrier or supermarket? Probably not. Once marketers pass that threshold the response rates are going to go down, absolutely."
Content must drive the show. If you have something to say each week or day or month, then a podcast will likely be positively received by your customers. However, if you're just putting together a show in order to say your name and product line as often as possible, you're likely going to actually do more damage than if you had done nothing at all.
What's that I hear? Is that Jon screaming "Content is King" again?