The beginnings of the graffiti and street art movement have been traced to the mid- to late-1960s in New York City, although there is evidence that it may have begun in Philadelphia at about the same time. Urban historians say the movement emerged from two factions -- political activists looking for a forum and street gangs staking territory.
The word graffiti comes from the Italian graffiato, which means scratched. It refers to work that is written, using words or symbols, and as a result, grafitti artists often are referred to as "writers."
Throughout its recent history, there have been strong arguments that graffiti is simply vandalism, an unwanted sullying of walls and public places; urban visual noise, at best.
The most common form, and the most reviled, is known as "tagging." A writer quickly scrawls his name, or moniker, on whatever outdoor, or publicly visible surface he can find, avoiding detection by the authorities in the process -- a quick-in, quick-out blitzkrieg of bus shelters, railway stations and billboards, leaving little time for artistic expression.
One particular individual known as Tox has been tagging on London's transport network for over nine years, usually eluding the London Transport Police and causing hundreds of thousands of pounds worth of damage, much to the frustration of London underground employees, such as Andy Hogg.
"Anyone that commutes on our trains quite regularly, I think, will have seen 'Tox,'" Hogg said on a Sky Travel documentary viewable on YouTube. "I don't know anywhere where I haven't seen a Tox tag -- on the walls, in the trains, in places even I can't access."
Perhaps the most famous renegade graffiti artist and "enemy of the state" to come out of London is the stencil artist Banksy, who, in earlier years, was pursued, unsuccessfully, by the police. He has now, however, become one of the most celebrated graffiti artists in the world -- with particularly iconic works, such as one depicting two police officers kissing. His pieces now sell for hundreds of thousands of dollars, although his identity still remains something of a mystery.
Tox is probably destined for lesser things. But while he may be thought of as a nuisance and a vandal, in extreme cases, tagging elsewhere in the world carries even more sinister connotations.
In Sao Paolo, Brazil, gangs have developed their own system of glyphs, a unique written language born from a lack of literacy that they use to provoke their rivals. Writing in territory that isn't theirs or writing over glyphs of a rival gang carries a de facto death penalty.
Young gang members with nothing to lose and a lot to prove take absurd risks to tag in the most inaccessible of places to bring further notoriety to themselves and their crews. There have been reports of some dying in the process, falling several stories while attempting to tag the highest levels of high-rise apartment blocks.
Unlike Sao Paolo's grafitti writers, proponents claim Buenos Aires' artists generally remain unconnected to gangs and criminal activities. Still, their origins may lay in troubled times.