Remember folks, sure video is generally more entertaining and definitely has its uses in marketing...but soon enough web video will be "old" and not as effective as it is currently (unless done correctly).
A simple audio still has the power to "market" just as well as video.
One simple advantage that audio has over video is:
You can multi-task while listening to audio!
With video you need your eyes AND ears open.
I've been listening to a whole bunch of IM audios lately while at work, and it makes the day go faster and I still have plenty of brain cells free to do my job
So have a think about your audience and how audio may sometimes be a better option than video.