Wikipedia has somewhat altered its anyone can edit policy to improve the quality of its service:
Those measures can put some entries outside of the "anyone can edit" realm. The list changes rapidly, but as of yesterday, the entries for Einstein and Ms. Aguilera were among 82 that administrators had "protected" from all editing, mostly because of repeated vandalism or disputes over what should be said. Another 179 entries--including those for George W. Bush, Islam and Adolf Hitler--were "semi-protected," open to editing only by people who had been registered at the site for at least four days.
While these measures may appear to undermine the site's democratic principles, Jimmy Wales, Wikipedia's founder, notes that protection is usually temporary and affects a tiny fraction of the 1.2 million entries on the English-language site.