The recent abundance of audio and video podcasts on the blogs of many professional hobbyists makes me wonder if they really understand their medium.

If you have something to say but nothing worth to show, then why don't you simply write it?

There simply is no point sitting in front of a microphone and/or a camera just to tell us what you are too lazy to write. Let's face it, most of those little clips have nothing to do with the original idea of the podcast which was to have some fresh content to listen on the go.

I find most audio and video posts not only embarrassing for their authors but actually very disrespectful for the audience. Well, at least for the part of the audience who cares about its precious time.

First, this content is not scannable which is the golden rule of web authoring. A nice counter-example is the pretty cool video interviews at InfoQ which allow you to skim through the questions. But that doesn't solve the other problem: speech is an inherently slow medium.
An average person can read between 250 to 300 words per minute (much more with proper training) while a casual conversation (which is what most podcast sound like) has an average of 200wpm.

Those two drawbacks are enough to make sure I don't even care to click play when I encounter such an thing.

Just “because you can” or because its “new” is not argument to bloat the web with unusable content.

All the folks who are pushing audio or video content thinking that they contributed to any kind of worldwide knowledge or discussion are actually impoverishing the web as a whole. They are just spreading noise that no search engine or aggregator can make a sense of (yet, I know).

While I'm in a sarcastic mood: has anyone heard about the latest development of the semantic web lately?