Supporters say it's an inspiring cacophony, but critics say it sounds like a swarm of bees, drowning out fans, commentators, national anthems and generally ruining the World Cup experience for everyone.
FIFA, the soccer-governing body in charge of the World Cup, is under pressure to ban the noise-maker. It said in a statement that for now it will only outlaw vuvuzelas if they become a physical hazard, such as if fans throw the horns on the field, but that it "continues to evaluate the use of vuvuzelas on an on-going basis."
FIFA president Sepp Blatter further clarified the body's position with a Twitter post saying, "To answer all your messages re the Vuvuzelas. I have always said that Africa has a different rhythm, a different sound....I don't see banning the music traditions of fans in their own country. Would you want to see a ban on the fan traditions in your country?"
In response to the criticism, South Africa's Johannesburg Star newspaper reports that Masincedane Sport, the company who owns the vuvuzela trademark, plans to offer a quieter version of the horn.
"We have modified the mouthpiece, there is now a new vuvuzela which will blow noise that is 20 decibels less than the old one," Neil van Schalkwyk, a partner at Masincedane Sport, told The Star. "We hope to sell these at park and ride areas and public viewing areas."
Studies have shown that the vuvuzela's noise is 127 decibels, louder than a drum or a referee's whistle.
Earplug sales in South Africa are reportedly high as fans become increasingly concerned for their hearing, and players and coaches have formally complained to FIFA about the horn. France's captain blamed the vuvuzela for keeping the players from hearing each other on the field.
Twitter is abuzz with tweets against the vuvuzela from fans in the stadiums and those watching at home. Facebook and other blogs have started campaigns to get the horn banned from stadiums.
Vuvuzela Supporters Launch Twitter Campaign
But vuvuzela supporters are just as emphatic that it's a very South African way of paying homage to the game. For South Africans, vuvuzelas are to soccer what hot dogs are to baseball. No game is complete without them. And they have countered with their own on-line campaigns. There's now even a Twitter hashtag, #SavetheVuvuzela.
Supporters with iPhones can download vuvuzela applications. The iVuvuzela app allows users to play a short vuvuzela drone by touching a button, and a Vuvuzela World Cup app that actually allows the user to blow into the iPhone microphone to make the noise.
"Going into a stadium without a vuvuzela is like going to war and being unarmed," Petey Mthethwa, a worker from Lumoss Mouldings, a vuvuzela manufacturing company in Johannesburg told ABC News.
While the exact origins of this stadium blower are disputed, legend has it that the plastic horn harkens back to a time when South African warriors blew antelope horns to call villagers to meetings, to announce their arrival at battles or to strike fear in the hearts of their opponents.
Many foreign fans at the World Cup have embraced the tradition. Vuvuzelas can be bought with flags and colors from other countries competing in the tournament, including the USA. And although South African soccer fanatics have no problems with it, foreign fans have had to put in effort to learn how to properly blow the instrument.
Getting the sound right takes some skill and a lot of lung capacity. A true vuvuzela cacophony needs legions of soccer fans with puffed-out cheeks, looking like Dizzy Gillepsie or Louis Amstrong, blowing their trumpets.
But the problem may be that too many soccer fans are actually getting it right, and the result, for many, is a nuisance.
A ban against the vuvuzela has been considered before. After last year's Confederations Cup, thousands of fans from all over the world sent e-mails and letters to the FIFA, urging it to outlaw the instrument from the World Cup.
Ultimately, however, it was decided that the the vuvuzela was "essential" to the African football experience.
Banning the horn, FIFA's communications director Hans Klaus told reporters last year, would be akin to taking away the cowbells from Swiss soccer fans and banning English soccer fanatics from singing.
"It will be a World Cup with African sound," said Klaus. He said he was convinced the vuvuzelas would be a "hit at the World Cup."
FIFA maintains that the vuvuzela, annoying as it might be, is considered too entrenched in South African culture to outlaw. That may change if the outcry from its critics becomes louder than the drone of its sound.