Not everybody is a fan of these. Personally, I think these are great ideas. Now that Measure S has been defeated, what would you rather have -- four units on one lot on your residential street, or a three-story, 18 unit condo complex on the corner? If we must shoe-horn more and more people into residential areas (I'm not sure we do, but everybody else says we do), this can be a great option that preserves neighborhood character. Just like the old-fashioned bungalow court apartment units. Fun fact: none of my buyers want one of these, but I expect that may change as homes get more and more expensive.
Photo above: 2872 Allesandro, L.A., courtesy of TheMLS.com