Blame is the accusation of another person or entity of having caused a bad outcome to occur. Ultimately, of course, causation involves a lengthy chain of events that originated long before we were born. Even now, there are many people who could be credited or blamed for any particular outcome; this was the point of the "For Want of a Nail" proverb, which describes a lengthy string of escalating events leading to a kingdom being lost, which could have been interrupted by many different people along the way. For example, someone could have taken care that there were enough nails to ensure that the shoe was not lost, or enough horses and riders that the loss of one would not cause the message to be lost, or that the overall strategy did not depend on that one battle being won in order for the kingdom to survive.
Judicial and political systems
Likewise, a person's going to prison is the result of many actions taken by many different people. Intellectuals influenced an electorate; the electorate elected legislators with particular views; the legislators passed a law outlawing certain behavior; a person engaged in the behavior anyway; a police officer arrested him; a prosecutor threatened to punish him more harshly if he did not plead guilty; the defendant pleaded guilty; the judge sentenced him; and the prison guards kept him in custody for the duration of his sentence, ensuring that he did not escape. If any of these events had not occurred, the chain of causation might have gone differently.
Indeed, one could just as easily lay the blame at the feet of those who could stop it from happening, but don't. For example, libertarians, even as a political minority, are numerous enough that it would theoretically be possible to engage in civil disobedience that would bring the machinery of the state to a halt. If such a determined group, willing to make the sacrifices involved in such an action, were to demand the release of certain prisoners, they might be able to impel the government to acquiesce. Might not their inaction be blamed, since omitting to do what possibly could be done is itself a form of action?
It is common to say to such people, "You chose to go prison." This is not strictly true; rather, the person chose to break a law, knowing that the behavior was illegal and that there were people out there who believed in punishing such lawbreakers and had banded together to form a government that would punish him if it got the chance. But the chain of causation involved many more actors than just him.
The question of whether wrongdoing has occurred, of course, is totally separate from the analysis of cause and effect. It is possible to be partly responsible for an occurrence and yet not be morally culpable. For example, a politician may brag that his crackdown on drugs put thousands of drug dealers behind bars. In other words, he is taking responsibility for what is regarded as a good outcome, viz. punishing lawbreakers. Yet if anyone complains that the drug dealers and their families suffer greatly from their imprisonment, he will argue that it is the drug dealers' fault that they are in prison. In other words, he is simultaneously claiming and deflecting responsibility for the ultimate outcome, viz. the drug dealer's incarceration.
Although both he and the drug dealer were involved in the chain of causation that led to the latter's incarceration, he views the drug dealer as the one who created a bad state of affairs (a situation in which drug dealing was occurring) while the politician took action that led to an outcome that, while imperfect (in that the taxpayers had to fund many prosecutions and incarcerations) was still better than the alternative, viz. allowing the drug dealers to ply their trade unhindered. The badness or goodness of different states of affairs is a matter of opinion and depends on individuals' subjective value judgments. For example, a libertarian might view the drug dealer's actions as a useful service to drug consumers, or at least may regard a state of affairs in which people are free to sell drugs as being preferable to a situation in which the government arrests people who engage in those transactions.
In any event, a person may choose a course of action and still not be responsible for the fact that the outcome was bad, even if he knew how bad the outcome would be. For example, Henry David Thoreau took an action, that of refusing to pay taxes, because he deemed the alternative of financially supporting slavery and aggressive war to be even worse. He then wrote an essay which contained certain complaints about the punishment he had to endure. There are many people who would say that people who find themselves in such situations for such reasons have only themselves to blame. But from the perspective of the acting man, the course taken was the least bad that he could have chosen. What he is complaining about is that he was thrust into a situation in which all of his available options were rather unsatisfactory.
Art Carden writes, "In modern parlance, don't be 'that guy.' When you identify a source of social tension, realize that the source of the tension might not be the ignorance, idiocy, or venality of the people you want to control but your desire to control them."
- Mises, Ludwig von. Human Action. http://mises.org/humanaction/chap1sec1.asp. "The vigorous man industriously striving for the improvement of his condition acts neither more nor less than the lethargic man who sluggishly takes things as they come. For to do nothing and to be idle are also action, they too determine the course of events. Wherever the conditions for human interference are present, man acts no matter whether he interferes or refrains from interfering. He who endures what he could change acts no less than he who interferes in order to attain another result."
- Carden, Art (21 April 2010). "Why Economics Is Crucial for Ethics". http://mises.org/daily/4252/Why-Economics-Is-Crucial-for-Ethics.