From an interesting review of David Garland's The Culture of Control in The New York Review of Books:
Crime continues to decline, though the US incarceration rate continues to rise (by 2.6 percent last year, the largest increase since 1999). As a nation, we could eventually be more deeply injured socially by mass imprisonment than by moderate crime. For imprisonment amplifies the alienation that so often fuels crime, particularly when imprisonment is so racially imbalanced.
...Has imprisonment now become the covert but official method of dealing with "disorderly" blacks in America, with capital punishment its extreme expression? Is "indifference" to the huge imbalance of blacks in our prisons less an expression of "indifference" than of denial, of wanting to turn away from the problems of race in America?
I don't agree with the reviewer's conclusions (or Garland's, for that matter), but the question of why the US has become such a prison-happy country is important and yields no easy answers. The same goes for the possible long-term effects of incarceration policies that increasingly throw more people in the clink.