Statistically, "number of things" articles have historically been bad content. Good writers don't structure their points as lists, bad ones do because they can't write well and so they can't segue from one to another effectively.
Full disclosure: I'm a Moz associate and a personal friend of Rand's.
Just an observation that this is pretty much a hi-touch version of clickbait. I'm sure your friend is a nice and intelligent guy, though.
I think there's a reason you don't see Harper's titling their Annotations like, "17 reasons CAN-SPAM is fatally flawed," but US Magazine does. I use these examples of meatspace magazines to counter any possible, "but it's the internet, that's the way people write there! dealwithit.jpg" No, it's just another instance of the same old thing discovered decades ago by Cosmopolitan and the National Enquirer.
I'm totally open to evidence to the contrary! What is some of the best writing you've ever seen that is structured as a list? If it exists, I haven't seen it.