This article is not very enlightening. It argues that the SEP has cracked the code on how to make a website that is authoritative, comprehensive, and up-to-date. You'll never guess how! All you have to do is get a couple of million dollars in grants, followed by substantial, ongoing financial support from a rich university, and then you, too, can maintain a website with over fifteen hundred articles! You just use all the money to cover boring stuff like hosting and pay several editors to keep the thing up-to-date and high-quality. Easy-peasy.
Now, don't get me wrong. The SEP is an absolutely fantastic reference. I have nothing but praise for it; I've found it very useful many times, over the years. But if it takes three editors to manage an encyclopedia with 1500 articles, then it would take a paid staff of over 10,000 editors to do the same for (the English) Wikipedia, not to mention the millions of people willing to guarantee their time over the course of decades to actually write the articles and keep them updated.
This is clearly not an apples-to-apples comparison. What wikipedia actually has is a 'staff' of about 40,000 volunteers who do a little work on the articles, most of which are much briefer and more restricted in scope (and, yes, far lower quality) than those in the SEP. The problem being solved by the SEP just isn't the same problem being solved by Wikipedia or the web as a whole, and it's mystifying that Sonnad pretends like the problems are comparable.
When trying to prove how bad Wikipedia is, Sonnad points out that it has fewer than 10,000 A-class articles (as compared to the SEP's 1500?) and so it's not really so comprehensive, after all. A better choice would be to Good Articles, which brings the total up to around 45,000. For comparison, the Britannica Concise Encyclopedia contains 28,000 articles.
Worse, though, Sonnad cites a post on Wikipediocracy (a site dedicated to criticising Wikipedia--hardly an unbiased resource!) in which an associate professor of mathematics, Adrian Riskin, complains about the Wikipedia article on polynomials ("I was relieved because my preconceptions about the general suckiness of Wikipedia were confirmed.", he writes--this being the usual academic approach to basic research).
It's an odd criticism. A couple of examples:
He admits that the articles on advanced topics are very useful in practice and he often uses them and so do his students, but then he complains about the article on polynomials being aimed at an advanced audience, when it should be aimed at "kids doing their homework". But Wikipedia isn't supposed to be a junior encyclopedia for kids, so...
He complains about the stated etymology of the word polynomial: "Polynomial comes from the Greek poly, “many” and medieval Latin binomium, “binomial”." Riskin writes: "And this is not only wrong, as the Oxford English Dictionary shows, but obviously wrong to anyone with a grasp of the Greek and Latin roots involved. “Poly” does mean “many,” but “bi” means “two.” There are also monomials and trinomials. If the word “binomial” has an influence here it’s as a pattern rather than as a root. But there are three citations, it must be true!"
Okay. But the OED says "Hybrid f. poly- after binomial (irreg. f. L. nōmen name)." and of binomial it says "f. late L. binōmi-us (see binomy) + -al1; cf. F. binôme." So, it uses a different form of that binomi word, but otherwise... agrees with Wikipedia?
That's enough time spent on these things. The takeaway here is that the SEP is great, and everyone should go have a look, but I'm not buying the criticism of the rest of the web in general or Wikipedia in particular.