From Walkable DFW blogger larchlion: "Richard Florida has a good, short post up arguing against what we might deem 'blind density'. In other words, in an effort to chase after density, we're simply building taller. Not more compact. And certainly not more efficient. "The diminishing returns comes from a few places. First, walkability and modal share of alternative transportation begins to jump around 20 units per acre. These gains in other, more efficient forms of transportation start to gradually decline from 40 to 60 units per acre and then plateau.
"Another issue is that adding height often diminishes the quality and character of a place. Not everybody wants to live or work in a high-rise. By adding density only via height, you're effectively adding supply while diminishing your market, aka demand.
"Density (should) = desirability. While I'm not totally against height or tall buildings (I live on the 19th floor currently), I am very wary of a rush towards adding height that might diminish the overall character of the place that makes it so desirable in the first place.
"Lastly, besides the role of density in transportation choice and reduced infrastructural load, the goal of density (mostly to economists) is to accelerate the internal combustion engines of cities, efficient and accelerated exchange of goods, services, and ideas within proximity. However, stretching buildings upwards has the same effect as stretching them outwards." Full post here.