An example from personal experience.

Reports on the humungous errors of the Wikipedia often make it to the mainstream media, but it's probably around the more mundane, and certainly less earth-shattering, entries that this sort of thing is widespread.

My brother has edited a Wikipedia entry only once. For some reason (around the time of Purim this year) he felt moved to add a possible explanation for the term to the already existing entry on hamentasch. His contribution was almost immediately edited out. This, of course, is legitimate, but the explanation given by the person doing the editing still raises a bit of an eyebrow. This person simply wrote:
Somehow, I don't think so.
and then added:
If it reappears, I'll add a cite tag.
Again, this is legitimate. And yet, in less than one day, my brother's more-or-less learned addition to an entry in the Wikipedia was edited out by someone who, writing about himself, tells us:
is just another guy with a bit of knowledge and time
He seems to devote most of his Wikipedia time to Stargate related entries, and seems to have no particular interest in linguistic issues.

It's my guess that this particular editor quickly lost interest in this subject since only a few days later someone else re-edited the entry, adding an explanation very similar to my brother's for the origin of the name.

Similar Wikipedia experiences have been reported numerous times - sometimes by people who have offered only one addition or edit to the encyclopedia, and sometimes by people who've been actively involved in the Wikipedia community. One commenter to Aaron Swartz's investigation of who produces the Wikipedia rather accurately echoes my brother's experience:
i love wikipedia. but i have felt that my contributions -- on topics where i do have expertise -- have been warped by people who merely want to "make it sound like an encyclopedia" without having any knowledge of the topic.
On the other hand, I have no objective means of determining whether this person's claim to expertise is legitimate.

Go to: Just who do you think you are?