Last week, yet another teenager died as a result of gang-related violence in London - the eighteenth this year.
An Independent on Sunday investigation suggested that almost 14,000 people a year are injured in knife attacks. Some authorities believe the number may be much higher, because many people do not report their injuries for fear of reprisals.
In gangs, like mobs, people will often do things they may never do on their own. In the UK, gangs are made up most often of boys or young men, aged 12-15 or 12-18, drawn mostly from the same or similar ethnic groups.
And gangs are by nature extremely territorial. Members will do almost anything - even commit murder - to protect an area, street or neighbourhood that they call their own.
For some young people, gangs represent excitement, risk, adventure. For others, they provide protection and belonging: there's prestige in wearing the gang's colours. For some, of course, gangs are about making money - which is why gang culture and drug dealing are so closely intertwined.
Some governments, in the UK and Europe generally, have tried to deal with the problem of youth violence with so-called zero tolerance penalties, including tougher prison sentences.
There's no doubt that, at least in London's case, more visible 'bobbies on the beat' might provide some deterrent against crimes of this kind. CCTV cameras can't take the place of police personnel. In fact, in many areas of the capital, many of the cameras don't work and those that do are relatively useless when it comes to actually preventing a crime.
Tougher measures law enforcement measures may also help to get some guns off the street, which would be great.
Yet on their own, these measures sometimes seem to make matters worse. It's as if violent kids feel the need to hit back even harder at a system that's out to get them.
Before we can find lasting solutions to the violence problem, we need to try to understand the psychology of violence. Some people who work on the front lines with violent teenagers put them into two categories: the "initiators" and the "imitators".
Initiators learn violence in an abusive or neglectful home. Sustained abuse affects their ability to exercise control, to express empathy and see the consequences of their actions.
In the end, they can't channel their emotions in a healthy way. In fact, studies have shown that with these initiator kids, it's the act of violence itself that has a calming or soothing effect.
Children who are physically abused in the home will often store up a deep need for revenge. As they get older and physically stronger they see the chance to make the shift from being underdog to "top dog".
They know they're less likely to be attacked when they're strong, so they put a premium on getting respect. That's what the gang-like designer clothes, jewellery and weapons are all about - respect.
Some violent kids talk about a kind of tipping point into violence. Something triggers a memory of past abuse and they suddenly feel propelled into a state of almost uncontrollable fury.
At the time, they don't really seem able to see or hear the people who are trying to calm them down.
If their victim pleads for mercy, it makes them angrier, because it reminds them of how defenceless they felt when they were abused.
Then there are imitator kids: those who come from ordinary homes and on the surface have no real need to be violent. They often become violent as a way to avoid being bullied; they imitate violence to get a higher power rating among their peers.
So what can be done to turn all this around? At the government level, I think, it would definitely help to have more support for the traditional family unit.
In some parts of the world today we have political leaders whose policies seem to support every definition of family apart from the traditional one, as if 'traditional' were a pejorative word.
It's very important, of course, that government funding supports things like single parent families. But all too often, I think, government handouts make the break-up of a marriage seem as practically viable as keeping it together.
And growing government support for same-sex partnerships and IVF for same-sex couples diverts much-needed funding away from measures that would strengthen the traditional family, which has always been the bedrock of society.
Some will argue that politics has no place interfering in marriage and family, or that you can't legislate morality. Actually that's what good law is, at its most fundamental level - the codifying of standards of behaviour based on solid, proven values.
Governments have a duty to show positive discrimination in favour of the traditional family, because time and again studies have shown that children experience fewer development problems when they have a father and a mother in a stable family home.
Governments must also show a much greater commitment to organisations that have a proven track record in helping troubled young people. Now, I know about this because I ran a very large national network for young people in Australia for a number of years.
Despite its size, success - it was the fastest growing youth organisation in the nation - our organisation found it difficult to get funding from governments. Why? Only because we refused to hide the fact that our values were based on faith.
Local governments could do a lot more, too.
A lot has been said about the need for sex education and even teaching about so-called "alternative sexuality". But in many areas very little has been done to provide training or counselling that would actually help young people deal with violent impulses.
Media leaders also have a role to play. Media producers and film-makers have long said that when they show violence they're not creating the problem; they're simply reflecting what goes on in society. I wonder, though, how many times you can reflect something before you start reinforcing it - especially in the pliable minds of children.
A number of studies have shown that repeated exposure to violence in the media actually desensitizes children. It makes them less likely to be horrified by violence. It also makes them less likely to intervene if they see someone else being victimized.
Of course, parents have a huge role to play - perhaps the most central role - in reducing gang violence. But without support governments and community leaders, many parents - particularly those who have themselves grown up in an environment of violence and abuse - find it difficult to cope with troubled teenagers.
Copyright Mal Fletcher 2008. Not to be used without permission.