Alex Balk at The Awl published a brief post against longform nonfiction storytelling. Here's a quote from the piece, which I think gets the point across with even more brevity: "Are there some stories so intricate that they actually demand tens of thousands of words to tell them? Sure. Maybe six or seven a year. Everything else you read is padding or awards-bait."
It's purposefully incendiary stuff, and obviously a broad generalization. Personally, I tend to prize pieces of a certain length; here at the Seattle Review of Books, we rarely publish reviews that are shorter than a thousand words, because we think anything less tends to fully fail to develop an idea. I recently wrote a piece for the site that was over three thousand words, but I hope to cut it down a little bit in the editing process.
But in general, I tend to agree with Balk; I've read a lot of longform pieces that have wasted my time. I'm fine with digressions and taking your time to tell a story, but a story should be exactly as long as it needs to be. We've all read magazine articles that have been puffed out to book-length; we all agree that those are terrible. When that happens, we feel manipulated, and it sours the reading experience. Same with longform. That said, I am always in favor of more writers writing more, and if longform is the vessel that gets readers in front of writing, that's a-okay with me.
But rather than arguing about a nonexistent perfect metric for exactly how long a piece should be, I'd rather everyone read this great post by Chuck Wendig about why paying writers is so important. It's titled "Scream It Until Their Ears Bleed: Pay the Fucking Writers," and it's in response to an idiotic Huffington Post editor's bullshit claims that paying writers is "not a real authentic way of presenting copy," that because Huffington Post bloggers write out of passion, their writing somehow has more merit. I don't know how many words Wendig's post is, but I can tell you it's exactly as long as it should be.