Capturing and Cultivating Wild Yeast for CO2 Production?

I'm researching the homemade CO2 generators and nobody ever mentions wild yeast. I've watched specials on Food Network about bread starters, and I'm sure you can keep a wild yeast culture alive indefinitely if you take proper care of it.

Has anyone tried or heard of this?

sourdough starter.
http://video.google.com/videosearch?q=sourdough+starter&hl=en&emb=0&aq=0&oq=sourdough#

Alton Brown-Dr. Strangeloaf
http://www.youtube.com/watch?v=FqxkMqsEQI0

Or is it possible to use instant yeast and propagate the culture to immense proportions?

Nobody? I think it's a cool idea. Sourdough Yeast Generator. Or like 8 of them.

I also heard you can clone yeast,

Or keep a huge culture/propagate instant yeast, to make future generations of generators...

Nobody?

eh, whatever.