An army of bloggers has been joined by celebrities including the singer Moby and the founders of Google and Microsoft to fight a decision in the US House of Representatives that allows telecoms companies to charge popular websites for priority access to the Web.
A law that would have enshrined the neutrality of the Net was voted down by congressmen late on Thursday.
Telecom and cable companies are in effect being allowed to erect toll booths along the information superhighway - and individuals who post their own videos or blogs online could find their websites confined to the internet's B-roads or even blocked altogether.
Instead of an anarchic free-for-all that has dramatically broadened free speech and democratised access to information, the internet would come to be dominated by the giant internet and media companies that could afford to pay to make their content most easily available, campaigners say.
The battle is shaping up as a clash between the corporate lobbying power of the telecoms and cable industries and a shambolic but powerful grassroots resistance movement fostered on the internet. That movement hopes that the US upper house, the Senate, will reintroduce the guarantee of Net neutrality into its own telecoms bill, which it starts debating next week.
Robert McChesney, founder of the savetheinternet.com coalition, said: "If we lose Net neutrality, we lose the most promising method for regular people to access and provide diverse and independent news, information and entertainment. We will see the internet become like cable TV: a handful of massive companies will decide what you can see and how much it will cost. Gone will be the entrepreneurship and innovation that has made the internet the most important cultural and economic engine of our times."
Savetheinternet.com and others are fostering a resistance movement on the Web, through community sites such as MySpace and on amateur video sharing web services like YouTube.com.
Meanwhile, Bill Gates of Microsoft has been pressing the issue with politicians. And Sergey Brin, co-founder of Google, was on Capitol Hill this week making his first stab at lobbying. Google started as an offshoot of Stanford University and grew through word of mouth, but it may never have got off the ground if it had to pay "congestion charges" in its early days.
Telecoms companies lobbied hard against the Net neutrality law, because they want to start charging popular websites for the large amounts of bandwidth they use. They contend that their cable networks will soon become congested because websites such as Google and even broadcasters are starting to offer video over the internet. Charging these companies is only fair, they say, and would generate cash to invest in upgrading the network.