Wikipedia

Wikipedia is "a multilingual, Web-based encyclopedia project, operated by the Wikimedia Foundation, a nonprofit organization."

I think that the source can be very valuable even if it can be edited.  As long as the information is checked and found to be true.  Information is always changing, and those well-versed in a subject would know well enough, I think, to find information and share it with others who also know the subject or are enthusiastic about it.

They trust the population of people who visit the site to weed out misinformation.  Those that have knowledge or have found sources that prove otherwise.

Larry Sanger left Wikipedia because he felt that more authority should be given to experts on the site.  He created his own site after leaving that did just that.

I have no idea what abuse or vandalism would look like on a Wikipedia page.  The article says nothing about it.

The statistics offered in the third paragraph of the article reveal that Wikipedia is quite a popular site with a good bit of information to be found.

I think Wikipedia is so successful because it provides a place to get a good bit of information on a topic.  Even when doing a project, though you shouldn't credit Wikipedia it is a great place to get a good idea about what it is you are researching and several sources that could potentially be used.

I would say that the founders would not want to accept advertising because the people and corporations that advertise on the site would likely bias some of the information found there.  They may want something to adhere more to their views than to let the people who visit see both sides of a situation.

Wikiscanner gives people a way to see who is updating information and how reliable they may or may not be.  It also makes people responsible for their actions and what they say or do on Wikipedia.