"We don't want a digital 9/11. Unfortunately, the risk is getting higher," says Andrea Pirotti, executive director of the European Network and Information Security Agency (Enisa).
Pirotti was speaking at the opening a summer school for policy makers, civil servants and private sector managers on online privacy and security issues in Europe.
The growing likelihood that a catastrophic failure of the internet will destroy users' trust is haunting European politicians and civil servants. They fear that with it will go the dream of an economically vibrant networked economy.
According to an Enisa document, there is a 10% to 20% chance that telecom networks will be hit by a major breakdown within the next 10 years, and that it will cost the world €193bn - roughly equivalent to the projected UK national debt, thanks to the banking crisis.
Moreover, European politicians believe the digital economy could generate up to three million new jobs in the next few years. This is on top of five million created by the mobile phone industry.
The EU funded the initial research into GSM, the mobile phone's most successful technical implementation, which now claims more than 70% of the market.
The European Commission has earmarked €18m to develop GSM's latest technology, LTE Advanced, which will permit handsets and other devices to connect at 1Gbps within four or five years, says Joao da Silva, director of the European Commission's network and communications directorate.
LTE Advanced will put mobile communications on a par with or better than fixed-wire systems for speed. Fixed-wire network operators will have to install optical fibre links to the home to stay competitive, he says.
But the foundations are fragile. The failure could come either from a technical failure or outage, or from a massive breach of personal privacy, says MEP Jorgo Chatzimarkis.
Consumer trust in the network is essential for the development of a networked economy, so the resilience of the internet is a European priority, he says.
This fear drives an EU budget of nearly €1bn for network and information systems R&D. Much of this is to improve the internet's defences against intentional attacks or accidental failures, but even more is to improve the user's experience and trust in the systems, he says.
The key application areas are to create smarter systems to enhance living, energy use, transport and health, he says. There are already many projects that use location and geographic information to manage these aspects better, he says.
This raises the issue of how much information people are willing to give up, or that governments believe they need, to fulfil this ambition.
Privacy is a fundamental human right, says Pirotti. But people are surprised how much of their lives leave an online "shadow", says former US National Science Foundation executive Peter Freeman.
Freeman was an early funder of the research project that turned into Google, and gave the go-ahead to the NSF's Geni project, a long-term project to allow researchers to do large-scale experiments on the social and technical development of next generation networks.
He is deeply worried that a catastrophic failure or other loss of confidence in the internet will provoke consumer demand that governments lock down the internet.
Quoting Harvard's Robert Zittrain, he says this would kill the element of play that has created so much wealth via the internet.
"You can never build the technical walls high enough," he says.
The real issue is changing people's behaviour. "We need the right legal and social defences against abuse," says Freeman.