Wikipedia, the online encyclopaedia, will go down as an internet pioneer. It operates on the principle of open access to all of its users – anyone can edit its articles. But now the site has formalised restrictions on the kinds of entries that new users of the site should be allowed to change unaided.

This seems to cut to the quick of what Wikipedia is about. The assumption underpinning the site was that, by asking its millions of readers to check entries, errors would be caught and “ ... usually corrected quickly”. The reality was a little more complicated.

Some areas, particularly politics, attract partisans and vandals. Hoaxers also had their say. These troublemakers' efforts overshadowed the considerable benefits of the accumulation of online knowledge in some specific areas, such as economics and science.