Cul-du-sacs make everything worse
Slate’s design blog covered cul-du-sacs recently, revealing the seemingly-obvious but often ignored fact that common suburban layouts make getting around harder:
The system makes just about every destination farther away because it eliminates the most direct routes between them. Connectivity counts: More intersections mean more walking, and more disconnected cul-de-sacs mean more driving. People who live in neighborhoods with latticeworklike streets actually drive 26 percent fewer miles than people in the cul-de-sac forest.
The point is that the spagetti-like streets of suburbia push destinations out beyond walking distance. The article also touches on the psychology of walking; people will walk different distances to different things based on how they perceive those things. For example people are willing to walk farther to get to the train than they are to get to the bus.
Things get even worse, the article points out, because the experience of walking itself has deteriorated:
Put simply, most people do not walk in American cities because cities have designed destinations out of reach. But they have also corroded the experience of walking. Road engineers have not even bothered to build sidewalks in many Atlanta suburbs. Try a Google search for directions near, say, Somerset Road in Mableton, and the map engine will offer a warning you would not expect in a first-world city: “Use caution—This route may be missing sidewalks or pedestrian paths.”
The same could certainly be said for parts of Utah, California where I grew up, and other places. As the article notes, aesthetics matter.
To give you a sense of how these things look, here’s an over head view of the Avenues neighborhood in Salt Lake:
The Avenues has fairly small blocks and streets (for Utah) and because it’s a grid offers a variety of route options for users.
By contrast, here’s a neighborhood just a few miles to the south:
In this neighborhood, distances are distorted because no one can chose a direct route.
As the Slate article points out, this is bad for health. I’d add that it’s also bad for the environment and the economy, as it contributes to pollution and costs people more to get around. And transit also will have a difficult time ever serving this neighborhood. In other words, this type of design makes everything worse.
About Town 
Have you considered that some families look for cup-du-sacs so their children can play in the cul-du-sac without the worry of increased traffic ?
Yes, but a good street is multimodal, allowing people, cars, to interact. If you’re afraid of traffic hitting your kids living in a more car centric neighborhood is the opposite of what you should do. Also, I’ve never seen any data indicating fewer auto-pedestrian collisions in cul du sac neighborhoods. In fact, everything I’ve read indicated the opposite is true.