I know everyone is sick of talking about Watchmen, but one of the more interesting plot points from both the comic and the movie was the fictional Keene Act, which outlawed unlicensed crime-fighting. The act didn't affect either the Comedian or Dr. Manhattan, who were already working for the government, but it did push Nite Owl II into retirement and turned Rorschach into an unlawful vigilante. Alan Moore was obviously commenting on the long history of superheroes as vigilante crime-fighters, but that begs the question, why were so many superheroes, particularly prominent ones such as Superman and Batman, operating outside the law to begin with?
The fact that most superheroes work outside the legal system is so normal to readers that few even notice it today, but there's no reason why superheroes can't be government agents (a few of them are), or lawful adjuncts of normal law enforcement (Batman was a deputized officer of the Gotham police for a few years in the 60s) , or otherwise answerable to some political authority. In real life, few people would tolerate private citizens dressing up like circus strongmen and fighting crime whenever they felt like it. And yet, such behavior is the standard in the superhero genre.
The popularity of the vigilante superhero is most likely rooted in the creation of the first superhero, Superman. Most people are probably familiar with the story of how two Jewish immigrants, Jerry Siegel and Joe Shuster, introduced the character in the pages of Action Comics #1 (1938). The politics of their early stories were unquestionably left-wing, with Superman basically behaving like FDR on steroids, helping the little guy while beating up crooked businessmen. However, one notable difference between Superman and FDR (besides the polio) was that the former pursued his objectives without any legal sanction. Siegel and Shuster may have admired FDR, but they wanted their hero to be unconstrained by bureaucratic red-tape or self-serving politicians.
Siegel and Shuster's creation was thus less a socialist ideal than a populist one. Superman embodied two related themes in American culture: individualism and a distrust of government. The central figure of American myth is the frontiersman, a rugged individualist and alpha male who deals with problems in a direct and uncompromising fashion. This guy doesn't care for sissy stuff like talking out problems and reaching a compromise. God gave him only one mouth but two fists, and he's gonna use 'em! But while Americans respect the frontiersman's aura of authority, they distrust any authority that comes in the form of government. After all, government is everything the frontiersman is not; complicated, corrupt, indecisive, and ineffectual. And there's the fact that nobody likes being told what to do.
Superman offered the perfect empowerment fantasy for American boys who were eager to escape a reality in which they were powerless. Here was a character who fixed problems, whether it be crime or run-down tenements, and he did so in a way that was immediate and concrete. More importantly, he took orders from no one, letting only his personal sense of justice dictate his actions.
The commercial success of Superman quickly inspired imitators, and the vigilante-as-hero became a genre convention. Batman, Green Lantern, The Flash, and later heroes such as Spider-man, Thor, and the X-Men all fought crime (and caused plenty of property damage) without permission from any governmental authority. Even after the birth of the Comics Code, when superheroes were supposed to be upstanding citizens who supported lawful authority, they never completely went legit. And in the post-Watergate era, even Captain America gave up on the government and became a nomadic biker (the heyday of his book, honestly). Then came the 80s, and the more the hero violated from the law, the better.
But we live in a post 9/11 world. The heroes who saved lives at the Twin Towers were not vigilantes, they were cops and firemen. Iraq wasn't liberated by Superman, it was liberated by U.S. soldiers. Surely there are people out there interested in reading about heroes who maim the bad guys with government approval.
Yet the two largest superhero publishers, DC and Marvel, still churn out the same superhero-as-vigilante stuff. This isn't because they're all anarchists who hate the government, rather both companies cater to nostalgic fanboys. Nostalgia is, for better or worse (actually, just worse), a major force in superhero comics. New heroes have trouble gaining fans in a market that's already saturated with decades-old characters with established fanbases. And older fans prefer reading comics that remind them of the comics they read as a child, in other words, comics about vigilante superheroes.
In 2006-2007, Marvel published a miniseries titled "Civil War," which affected numerous titles set in the Marvel superhero universe. Civil War ended with most of the heroes agreeing to work for the government-sponsored Initiative, headed by Iron Man. A handful of heroes, including Captain America, refused to submit. Civil War could have been the beginning of a shift away from vigilantism, but instead it was little more than a brief interruption in the usual status quo. As of 2009, the Initiative is now run by Norman Osborn, formerly the Green Goblin, Spider-man's archenemy. All the true heroes are now outlaws, and those who still work for the government are not simply sell-outs, they're villains!
So is the continued vitality of the vigilante superhero a bad thing? Probably not. It is just escapism, after all, and we haven't seen spandex-clad lunatics fighting crime in real life just yet. On the other hand, there is this guy.