While it is probably true that a more hostile environment is to blame for a big portion of the decline, the maturity of the articles might also be a factor.
Maybe the articles people care most about are sufficiently well written. Many people can't add much valuable information to a lot of the topics and so they don't feel the need to participate. Without this first quick win, there is little incentive to keep editing.
Yes, "Volunteers Log Off as Wikipedia Ages" is a much better headline than "Volunteers Log Off as Wikipedia Improves" (when "better" is defined to be "attention grabbing").
Even the HN headline does this: "Number of Wikipedia editors steadily declining". Maybe it should be "Quality of Wikipedia articles steadily improving". Which is the cause? Which is the effect?
The article says "Indeed, Wikipedia remains enormously popular among users, with the number of Web visitors growing 20% in the 12 months ending in September, according to comScore Media Metrix." This would indicate Wikipedia itself is gaining in popularity even as the WSJ headline implies it is going downhill (precipitously, I might add).
FWIIW, I've tossed in my 2c occasionally, but only as an anonymous contributor. I don't contribute enough to qualify as an editor, but sometimes a fact is wrong, needs clarification, or some English is rough. So, is there any metrics of anonymous contributions? Are they up? Are they down?
Beyond that, the article is full of anecdotes of Things That Went Wrong (but were corrected). How is that not a success story? If nothing went wrong, it would be because nothing was contributed. For the risk adverse, the "optimal" trade-off of risk vs. change suppresses all change (this is endemic in large corporations).
Then the rest of the article rolls out the same old criticisms of lack of credentials among Wikipedia editors.
Those who say it cannot be done should not interrupt those who are doing it
-- Chinese Proverb
In my experience, it is more likely to be the immaturity of the articles that is putting people off.
I have contributed a few edits to Wikipedia over the years. Why not, if I can usefully fill in a blank and it costs me mere seconds to help?
More recently, though, I've been finding subjects where the entire article was so hopelessly wrong that I wouldn't know where to begin fixing it, other than deleting it completely and starting over. I looked for an appropriate marker in one case that would at least suggest that the article as a whole did not represent a neutral point of view or was completely unsupported by any factual evidence, but after a few minutes trying to navigate Wikipedia's absurdly overcomplicated self-documentation and finding nothing but reasons I wasn't allowed to fix anything or contribute, I gave up and found something else to do with my time.
I wonder whether the neutral point of view principle isn't a significant part of the problem. Many of the pages I find most misleading are deadlocked, because no-one can agree on what a neutral point of view is.
Under those circumstances, perhaps it would be more helpful to do what civilised discussion has done since forever: present two articles (or sections in an article) that, by construction and intent, take opposing viewpoints. Let the reader see both sides of the debate, making the best case they can and with the best sources they can find to support their point of view, and let the reader decide. As long as it is very clear when there is a single article trying to present a subject neutrally and when the adversarial system is in use, I don't see why this would cause a problem, and it would break a lot of the deadlocks I've seen and get constructive editing going again.
The goal of Wikipedia isn't truth, it's verifiability. Whether it's possible to be truly neutral or not is besides the point. NPOV isn't a policy designed to converge on truth. It's a policy designed to converge on a set of verifiable statements.
I think the problem comes when you start to stray from objective facts, which really are inherently neutral, and get into more subjective evaluations of those facts or outright personal opinion.
On the tricky pages I encountered, often the problem was that the material was presented as a description of something, followed by advantages and disadvantages sections, and while the description may have been factual, that's where the objectivity ended. Perhaps from Wikipedia's point of view that means the pros and cons simply shouldn't be featured.
Realistically, however, someone researching a new field will probably be interested in such information, and many pages on Wikipedia do have this structure. Rather than trying to push water uphill, it might be a smarter move to adapt to the reality and do it properly.
There is a process of nearly mechanical editing you can do to fix subjective "Criticisms" or "Controversy" sections in WP articles: you replace naked opinions with overt citations, like, "In 2007, David Broder remarked in the New York Times that...".
There is also a fairly straightforward process of assessing the weight that a "Controversies" section gives to a POV by repeatedly citing similar or related sources, and a set of editing tactics that can be used to collapse them into a summary graf.
Maybe the articles people care most about are sufficiently well written. Many people can't add much valuable information to a lot of the topics and so they don't feel the need to participate. Without this first quick win, there is little incentive to keep editing.