I'm just going to talk about MP3 files here, but the same principles apply to pretty much any other type of audio file as well.
The most obivious example of meta data are the ID tags within MP3 files. The most obvious use of these tags is to scroll the name of the show and perhaps the artist across the screen of a digital audio player. In general, the more advanced the audio player, the more tags it can make use of.
If you're not in the habit of filling out the ID tags on your MP3 files, then you're probably missing out on some listeners. Since so many players and podcatchers are designed to make use of this meta data, your show may be problematic to your listeners and they may be unsubscribing to avoid the trouble.
There's a good piece on this over on Awakened Voice.
