The attack by student protesters Thursday evening in London on a limousine carrying Prince Charles and his wife Camilla, the Duchess of Cornwall, offers some broader conclusions. None of them are, as some commentary has suggested, that we are on the verge of a new era of protest with students in the vanguard. My alternative lessons:

Security threats can emerge from just about anywhere. The main theme in commentary in Britain about the incident is recrimination over a breakdown in security. “How could this be allowed to happen?” is the most frequently asked question. Investigations and inquiries no doubt will retrospectively point to some error in judgment about the route selected, or some shortfall of communication between the royals' security detail and other police elements. But even with terrorism—which this incident was not, although it could have been—the potential sources of threat are multitudinous. When non-terrorist agents of disruption such as rowdy students on a London street are factored in, the potential sources are essentially infinite. Even meticulous preparations cannot allow for them all.

Narrow self-interest can be behind wider trouble. Far from being the harbinger of a big new social movement, protesters who assaulted the royal limo and have been involved in other recent disruptions in Britain are overwhelmingly students upset about one very specific measure in the coalition government's austerity program; the raising of university tuition fees. Similar issues help to explain why there have not been protests in the United States against its current wars that remotely resemble those forty years earlier over the Vietnam War. The different magnitude of the wars and the number of casualties is one difference, but the presence or absence of conscription—and how it affects the personal interests of college-age males—is clearly another.

The line in any society between civility and disorder is thin and fragile. The political scientist John Mueller has made this point in studying genocides in Rwanda and the former Yugoslavia, in which a relatively few thugs were able to involve broader communities, at least as accommodating by-standers, in large-scale butchery. “Thugs are everywhere,” he says, “and only small numbers are necessary if the conditions are ripe.” As for conditions in Britain, Mueller notes, “England may seem rather tranquil and well-ordered in many respects, but it also is the home of some of the world's most notorious soccer hooligans.” The student protesters are a better educated version of the soccer hooligans. It is a long way to genocide from a broken window and thrown paint on Charles and Camilla's Rolls-Royce. But with any move from debate to damage, from the philosophical to the physical, there are no further strong firebreaks short of potentially highly destructive scenarios.