It is 20 years since the Web went live on Berners-Lee's desktop at CERN, with one web site and one web browser on the same PC.
This Scientific American article provides a non-technical and thorough overview of what sets the Web apart from most other technology infrastructures - principally its openness, simplicity, ubiquity, and the way in which the standards that shape its operation are governed.
Berners-Lee spells our clearly some of the emerging threats to the Web as a decentralised, egalitarian, open, and public resource. These threats include the "walling off" of information posted by users of social networking sites, interference by ISPs in which kinds of content get priority (i.e. absence of net-neutrality), and monopoly (when, say, one search engine, or one browser, or one social-networking site become overly dominant).
Berners-Lee does an important job as a figurehead in summarising the threats, but he is more-or-less silent on what to do about them. I can think of three reasons for this. 1. The Scientific American is probably not the place for a call to action. 2. What to do depends so much on where you live and what your role is. 3. The World Wide Web Consortium that Berners-Lee heads is complex (and I would guess sometimes uneasy) coalition of businesses and agencies which will not speak with one voice.
From a UK perspective, a key problem seems to be the Coalition Government's unwillingness to enforce net neutrality, evidenced by the disappointing "ISPs should be able to manage their networks to ensure a good service and have flexibility in business models" in this media release for a 17/11/2010 speech by Communications Minister Ed Vaizey.
One way for UK readers to "defend the Web" is through membership of and support for the Open Rights Group.