Vandalism's silver lining
editTo the extent that vandalism highlights the fact that anyone can edit any part of Wikipedia at any time, and keeps the community from taking itself too seriously, it is like actively encouraging people to find bugs in one's software -- it tries to maintain reasonable expectations and levels of effort.
Many closed-door productions are, in contrast, able to splash a veneer of formality and style onto their results by adding the names of a few luminaries to an advisory board and improving the quality of the paper used in the print run. Vandalism, like anonymous editing, is useful for its bold, insistent repetition of the mantra of openness.