Abortion and Crime? Related?

A recent book titled Freakonomics by Steven Lewitt. This contriversal book is aboutthe hidden economics behind every day problems in society. One chapter of the book has become a large dispute between economists everywhere. The chapter deals with abortion and crime rates. The theory, quoting the artical, "Unwanted children are more likely to become troubled adolescents, prone to crime and drug use, than are wanted children. When abortion was legalized in the 1970s, a whole generation of unwanted births were averted, leading to a drop in crime nearly two decades later when this phantom generation would have come of age."
Some economist are now saying that Lewitts reasoning is very faulty. And that he left out some major points to consider. After reading this artical do you think that this is a good theory or has Lewitt got it all wrong? What do you think is the reason for the crime drop?