Known as behavioural targeting, the practice has provoked a European Union lawsuit against the British government and sparked a number of US congressional hearings. Speaking at a web conference in Madrid yesterday, Tim Berners-Lee added his voice to those concerned about the potential impact on privacy of behavioural targeting systems that attach directly to an internet service provider's network.
"I just want to know that when I click on a link it is between me and the web, and the internet service provider is not going to immediately characterise me in different categories for advertising or insurance or for government use," Mr Berners-Lee said.
"The postman does not open my mail, the telephone company does not listen to my telephone conversations. Internet use is often more intimate than those things."
In 1989 Mr Berners-Lee proposed to colleagues at the European Organisation for Nuclear Research (CERN) the creation of the internet as a means for scientists around the world to stay in touch. He joins a number of internet and privacy experts in speaking out against behavioural targeting, which tracks web-surfing patterns of individual users and then uses the information to serve up specific advertisements.
Proponents of the technology argue it will increase the effectiveness and profitability of online advertising.
Market researchers and media advisory firms, including BernsteinResearch, Veronis Suhler Stevenson and UBS, have forecast slowing growth in worldwide online ad spending this year.
Two of the most high-profile developers of behavioral targeting systems that attach directly to ISP networks are the UK's Phorm and US-based NebuAd, both of which have attracted intense scrutiny over the past 18 months.
UK telecommunications giant BT found itself the subject of a City of London Police investigation last year after it was alleged the company had failed to adequately disclose to its customers trials of Phorm's Webwise system.
In October, BT said it would press ahead with more trials of the technology, and Virgin Media also said it was considering using it.
BT's previous tests in 2006 and 2007 drew wrath from the European Commission, which began legal action against the UK government earlier this month for alleged breaches of data protection and e-privacy rules committed by BT.
"There is an undeniable risk that privacy is being lost to the brave new world of intrusive technologies," EU telecoms commissioner Viviane Reding said at the time.
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