Yeast is swirling all around you, wherever you are, it is in the air. It is attracted to certain things, Like moist wheat flour, grape skins. In my opinion wild yeasts taste better. Here in Sacramento, we get the winds that just blew through San Francisco a few hours before. I don't see the big deal about San Francisco sourdough myself. Sourdough being readily available anywhere on the planet, and the particular yeast in SF given it's own Latin name, I guess it has a distinct taste, I don't know, I have only cultivated yeast here in my kitchen in Sac.