As I said, there are SIG's who are very, very protective of their subjects. If you look at the tabs across the top of any Wiki page, you will be able to look at the History of edits, Discussion between members etc.
If you find an item of information which is wrong, needs deletion or modifying, you can put it up for discussion with other members who share the same interest in the subject.
A minuscule example of SIG's here at:
http://en.wikipedia.org/wiki/Wikiped...ject_Australia
You will find a list of Australian topics being worked upon. These people involved are very dedicated volunteers, like the thousands around the world.
I feel Wiki has a "self-levelling" approach to it's accuracy of information. there will be a few sporadic errors but the overall effect of constant finetuning evens out the percentage of errors.