This is the purpose of a ‘wiki,’ based on the hawaiian word “wikiwiki” which means ‘quick.’ It’s a system set up on the basis that the community intelligence will eventually rise above that of the individual.
KellyM is quite right there are individuals who have been banned and pages which have been locked, but those both are very small minorities of the whole.
Thanks. What pages have been locked? Why? Too controversial?
The front page is locked, as is everything in the MediaWiki: namespace (which comprises various system messages and other things that are really tempting to vandals). Certain heavily-used templates are also locked, again, because of the high level of temptation presented to vandals. Individual pages will be temporarily locked to deal with especially egregious vandalism or to put the slapdown on an edit war. Such locks are normally only long enough to divert the problem.