Wikipedia edits apparently declining, peaked in early 2007
en.wikipedia.org
en.wikipedia.org
The problem is that people get bored and move on. The most intelligent people in society are no longer interested in politics. Which is why politicians today suck.
The most interesting thing going on today is tech, and within tech for a couple years it was Wikipedia. A couple years ago if you went into the Wikimedia IRC channels it was a mix of famous VCs, bestselling authors, and 14-year-old kids who spoke a dozen languages. Today it's just a bunch of bored librarians. The core community is off starting companies and writing books and whatnot.
It wouldn't surprise me if a sizable chunk of former core Wikipedians were now reading this site instead of making edits.
It seems to me that when our system of government was new it really was the most interesting thing going on so it attracted a lot of super smart people. Now, not so much. Of course part of it is that politicians have figured out it's easier to get elected if you pander to the lowest common denominator, but that still doesn't explain why a good percentage of them don't know how to use email.
Topics that fill books are given a few pages on Wikipedia. Niche content sites like MathWorld are usually much more in depth, but targeted at experts.
But I think it's important the point out that a peak in rate of edits doesn't mean the content stops growing.
However, that means for those topics, people will have to start learning more in-depth things to contribute, or the experts will have to start contributing.
I don't think there's a limit to human knowledge. It might just be an indication that there's nothing new going on recently. Once a new field or topic opens up, I think we should see another explosion of edits.
In the meantime, it'd be interesting to see the edit rates for the other wikifactions, like wikitextbooks, wikiquotes, wikitionary, etc. Maybe the activities have just moved over there.
If this talk on lexicography is any indication, there's still a lot of work to be done in other knowledge domains. http://www.ted.com/index.php/talks/view/id/161
One of the points of the talk was that dictionaries need to be updated in form--it's been the same since Queen Victoria I. http://www.confusingwords.com/ was a related website that I stumbled upon soon after. It'd be interesting if wikitionary would be able to incorporate not just meanings of words, but new connections between words, besides just being related in meaning.
If wikipedia is really serious about growing, they might do well to start figuring out how to progress from being merely a place to manage existing knowledge, towards being a vehicle/engine for developing/creating new knowledge.
Why wait around for new fields to open up? Start encouraging users to stick around and do it there...
I don't think it'd be hard to get more contributors to Wikipedia. Even after all these years you still have to be a geek to really use it, which is a total disgrace IMHO.