I have recently come back from a trip to Europe, which included touring around Italy and spent three days in Positano on the Amalfi coast (30 km from Naples.
In one of the local stores I found a jar of "Il Miracolo di San Gennaro" tomatoes (pomodorini in this case - the small ones rather than the San Marzanos).
I started talking to the shop owner (me not speaking much Italian, if any.. but made do with sign language, his broken english etc) about tomatoes and that led on to pizza in general, wood fired ovens etc..
The shop owner seemed highly amused that some guy from New Zealand seemed as passionate about pizza as them (Italians).
I explained to him that I use a natural starter for my dough and used the word "crisceto" (that I picked from Marco on this forum). He seemed amazed that I knew about this and he talked about the fact that in the "old days" all pizza dough was made with crisceto and how the use of a crisceto accounted for the flavour of the base..
He then said to me: Do you know how they make the crisceto?? I said "No" and he then told me they make the starter from a mixture of flour, water and Horse Dung!!!!
I didn't quite believe what I heard, so I made sure by getting him to repeat it a few times and he was very adamant.
This is most likely some sort of Neapolitan urban myth.. but thought it was intereresting to share the tale.
I have thought about this a few times since then and suppose that theoretically it possible. Wild Yeast is pretty much everywhere around us and by the time that you have gone through a number of feedings of the starter, there won't be any dung left in the starter anyway.
I am not going to try and replicate this myself (I am happy with my Italian starters from Sourdo.com) but if somebody else wants to have a crack, keep us posted... LOL