On the other hand, McLennan isn’t sure that the demise of the old model is a tragedy when it comes to arts coverage. “Traditional journalism has done a crappy job of covering certain kinds of arts,” he says, pointing out that dance, in particular, has been badly served. Nor do readers necessarily get the best deal when a single voice monopolizes the conversation: “If you’re in, say, Kansas City, and there’s a critic writing about an art form, and that’s basically the only voice you’re getting over a long period—well, even if he’s really a good critic and you enjoy him, it’s only one perspective. If there’s suddenly many people talking about that art form in a variety of ways, including online, and they’re debating it and bringing their knowledge, their experience of it, that’s very different. A lot of it is not going to be great. But a lot of traditional criticism has not been great.”

The failings of one school of arts journalism may not justify the failings of another. Yet, as Leon Wieseltier, the literary editor of The New Republic, points out, “Criticism is always in crisis.

“Every crisis in criticism supposes that it is unprecedented, he says, but now there really is a new reason for alarm. Criticism has always been a mixture of opinion and judgment, judgment being something more learned and more seasoned and more intellectually ambitious than mere opinion. But beginning with Amazon, which made anybody who could type into a book reviewer, and now as the Web sites and the blogs have proliferated, we have entered a nightmare of opinion-making. This culture of outbursts, and the weird and totally unwarranted authority that it has been granted, has been responsible for a collapse of the distinction between opinion and judgment. It’s one of the baleful consequences of the democratization of expression by the Web.

“I cling to this very old, sentimental, but not at all unrigorous Arnoldian idea of criticism—that the criticism of art is in some way the criticism of life,” Wieseltier says. “If it’s true that scarcity is the origin of value, then serious, extended, learned criticism is now more valuable, not less, and I have an almost religious belief in its survival, though in this thoroughly un-Arnoldian climate, I sometimes feel like a holy fool.”

David Hajdu is a professor of arts and culture journalism at Columbia's Graduate School of Journalism.