Wikipedia appears to be a valuable reference tool for usenet discussions. The importance of a neutral reference tool with (always improving) factual accuracy, especially when dealing with controversial subjects that are frequently discussed at usenet, is extremely high (Some of these discussions are denounced as "partisan wrangling" by some wikipedians, but are nonetheless significant for their participants).
Some usenet posters are extremely knowledgeable about certain fields and could have a lot of value for Wikipedia, for example, in a long sci.environment discussion about global warming, A debate related to climate change has been taking place that had significance for its corresponding Wikipedia article. The main points of the debate have been edited into Wikipedia by a conscientious poster. This is an example of how Wikipedia can serve as a reference tool to summarize discussions of controversial topics that are frequently debated at usenet (And also serve as an excellent starting point for them, or even replace them altogether!)
alt.food.vegan seems to have adopted the vegan recipes articles to document and exchange vegetarian recipes, this is also an example of how Wikipedia can be harnessed by usenet while expanding the written human knowledge.
For a recent list of Wikipedia citings, see this search on google archive