As posted in the thread on bee keeping, at least one other poster thinks of urban livestock as fad. Working on a sustainable code for Greensburg, I wanted to throw in all the current thinking. Many in Greensburg have very close ties to the nearby farms, often a relative still operates the old family stead. No one had any problems with urban horticuture. When I suggested urban livestock the nearly unanimous response was that they left the farm to get away from all that (stuff).
I discussed the benefits of raising chickens. One response was that neighbors might not care for decapitation next door. Another said "if it is chickens now, later someone would bring in guineas and turkeys--and you know what a problem they are". (Everyone appeared to know the problem with guineas and turkeys.)
I have fond memories of growing up on a farm. Mucking out stalls, creating a manure pile, letting it compost, spreading it on the soil for fertilizer. I also remember that our house was on a hill above all the crap. I remember my dog killing my goat. I remember trying to clean out a chicken coop.
Proponents of urban livestock do not seem to know all these values of farming. Either they think that all participants will be as tidy and caring as they are...or they expect code enforcement to handle any "issues".
I suspect that communities embracing urban livestock will in a few years be wringing their hands, trying to find ways to solve the "problem".