Some 7,500 people demonstrated Saturday in Berlin to express their concerns about personal data privacy as the German government and private companies amass giant databases, organisers said.
Called out by numerous civic organisations and political parties under the banner of "Liberty Instead of Fear!", the protestors denounced a government database which will collect information on wages, taxes and social payments.
They also protested against electronic passports, electronic health insurance cards, and an accord allowing the United States to access EU banking information as part of anti-terror efforts.
Personal and data privacy are sensitive issues for many Germans given their experiences under Nazi and Communist dictatorships.
Google's Streetview, which lets users view panoramic street scenes, ran into strong opposition in Germany, where many found it too intrusive.
Eventually the company allowed Germans to block publication of images of their residences, the only country out of over 30 where the service is available where users have such an option.
Germany's consumer minister, Ilse Aigner, in June deleted her Facebook account in protest at the networking site's inadequate privacy policies.
Explore further: Facegloria: Facebook for Brazil's Evangelicals