The issue of what they call 'detached accessory units' - or ' backyard cottages' in single family neighborhoods is an interesting one in zoning. For me it epitomizes the debate between growth and the preservation of historic single family neighborhoods.
The Seattle Times writes on the latest proposal from the City of Seattle, most interesting are the comments.
FWIW, I wonder how much more desirable Cities would be for living if instead of developing all these detailed rules we got rid of the control freak 'urban' bureaucrats?