This artcle from the Washington Post describes Virginia's new rule on cul-de-sacs; any new subdivision must have "through streets linking them with neighboring subdivisions, schools and shopping areas." The article goes into quite a bit of detail on the pros and cons of the cul-de-sac setup. Basically the pros are a quieter environment for those living on it, and possibly some increase in safety since anyone who's not from a neighborhood will look out of place within it. The cons are increased traffic, which leads to increased paving costs, not to mention the isolation and car dependence such setups foster. The increased traffic gets jammed onto arterial roads, which then become unsafe and/or gridlocked. In addition, they tend to isolate neighborhoods from each other, leading to a loss of a sense of community.
Getting rid of cul-de-sacs tend to improve cycling and walking conditions, by enabling cyclists and pedestrians to travel to places through quiet neighborhood streets. In terms of safety, it's quite possible that if examined rationally, the improvements from a cul-de-sac can be outweighed by the health benefits of an active lifestyle. The added risks of increased (car) travel may also weigh against the advisability of cul-de-sac living.
I've heard it argued that many people irrationally choose suburban living for its (real or perceived) safety from crime, but neglect the increased risks due to the increased mileage travelled by car. Apparently being a car wreck victim is somehow not as bad as being a violent crime victim. The truly rational assessment of risk is notoriously difficult, and it's something that people regularly ignore.
Finally, since the policy is a statewide policy for Virginia, one can't but wonder whether such would be a good idea to implement here and/or nationwide.