Among a large group of people, who is best qualified to promote a person to a position of authority or responsibility? Where I live, we hold elections to decide who will lead us and who will assume special responsibilities for the community. With more people participating in the election process, the responsibility for promoting a person is distributed. A single person is not responsible for promoting the wrong person; the blame rests equally on all who voted. As I see it, the reasoning is that the aggregate decisions of many people are more reliable than the singular decision of one person.
If so, the same idea is also relevant to large online communities.
For example, consider a large online community like Drupal.org--over 6000 users strong by my estimate--with multiple levels of responsibility. Levels of responsibility could include Forum Moderator, Book Review Editor, and Project Leader. With thousands of users available with varying levels of credibility, who can decide which user is suitable for a role?
An election takes the pressure off the Site Administrator. This implies a level of trust in the judgement of the community, of course. But no longer is the Site Admin responsible for gauging the quality of candidates for a role. Instead, the candidates must convince other people of their suitability. The candidate would have to persuade a percentage of the community or perhaps just a certain number of people. In the case of Project Leader the project's group members would be the community, and in the case of Forum Moderator every user would form the community.