The answer, obviously, is that they're all controversial. And (as measured by talk page size) they're the top-5 most controversial articles on wikipedia: see [[Wikipedia:Database reports/Talk pages by size]] (I'm discounting #1, "Main page", for the obvious reason). The only surprising entry in the top 10 is #10, Prem Rawat, who I've never heard of outside wiki. But he's some quasi-religious figure, so it makes sense. Chiropractic and Homeopathy make 11 and 12. And so on.
I found this page via the ever-popular arguing about the [[Monty Hall problem]] (if you've never seen the problem, do go and have a look but don't come back here afterwards and talk about it because we did that stuff in first year maths at university). That's followed by [[Climatic Research Unit email controversy]], so GW gets two in the top 20. But then its not till #43 that we reappear with [[List of scientists opposing the mainstream scientific assessment of global warming]].
I think its nice that 0.999, and speed of light, are in the list too.
* Hutzler 571 banana slicer - reviews.
Oddly enough, I just commented about this in Rosenhouse's "Counterintuitive Math Problems" thread, but I have an interesting perspective on the MHP.
I wrote and still maintain (for a value of "maintain" being approximately "continue to pay for the hosting") the first MHP page on the web — I first write and placed it on my personal site in 1996. It's usually the first or second Google result for the MHP.
With regard to Wikipedia, one big reason why I've never comprehensively re-written my page is because there are so many good resources on the MHP these days, not the least the Wikipedia entry. My ideal page would mostly be recapitulating much of what's on that page, and include one or more simulations — simulations which are available elsewhere and are linked from the Wikipedia page.
This wasn't always the case; I've watched that page grow from something minimal, less helpful than my page and mostly about the history of the published controversy, to a really good resource for ways to approach the problem such as will achieve genuine understand, both intuitive and technical.
And the talk page doesn't really show that much controversy or contested edits. At this point, it's mostly people arguing whether or not anything less than a strictly rigorous conditional probability analysis is actively misleading (and although my page is vulnerable to this criticism, I think it has merit), and pretty much not at all representative of the folk that are absolutely certain that it doesn't matter which door one chooses.
I tend to think that Wikipedia gets a bad rap, even within the narrow context of highly controversial issues (which, as you note, account for most edit wars and related inaccuracies).
I'm far from some tech/crowdsourcing triumphalist, I tend to agree that authoritative curated references are, all things equal, going to be more reliable.
But I think that it's an underlying, corrosive problem when people rely upon particular sources rather than their own developed critical faculty. For me, Wikipedia and the web in general represent a vast increases in research resources from which I can utilize my critical faculties and find some approximation of truth. There's false or badly misleading information in Wikipedia articles; but then, there's false or badly misleading information everywhere. I'm not arguing that there aren't more or less reliable sources; but in the absence of one's developed critical faculties, how does one even feel confident in determining which resources are more or less reliable, assuming that one was determined to insist that such a resource (or handful of resources) be exclusively authoritative?
But this is all sort of related to what I wrote on Rosenhouse's blog about the MHP: I've had sixteen years of correspondence with MHP skeptics and I'm still flabbergasted when one of them tells me that they don't even need to take the time to trivially test their intuition empirically because they know they're right. I've honestly, genuinely, tried to wrap my head around this for not only these sixteen years in this case, but my entire life, more generally.
At the risk of psychoanalysing, somewhere in this is the fear of being wrong, which results in a fear of self-doubt. We all have this to some degree; but I think a not-insignificant portion of people have this sufficient to require them to have a relatively very aggressive posture in defense of their certainty. Those folk surely account for 85% of the people fighting edit wars on Wikipedia. Some of those people are actually right, of course. But I don't think that being actually right, or being actually wrong, is a prerequisite for being the type of person who cannot stand the fact that there's someone "wrong on the Internet".
Apparently the Monty Hall dispute is not so much about the facts, more about how to explain them clearly. Honestly, I sympathize with the editors - it's a tough one.
Irrelevant note: Personally I have found it funny that ID, I.D. and Id have the same letters.
Somehow I find it amusing that "speed of light" *is* # 99.
But is being controversial enough?
Looking at the list I'd say the top topics tend to have ideologues among their editors - either to promote a point of view or suppress a point of view.
Of course, there can be ideologues on both sides of an issue.