So when does an article become an advertorial? When there's money involved, right?
When a dozen other low authority sites write about the same thing and link to the same site, and they have a pattern of doing this regularly.
This happens a lot in the fairly new blog tour scene, and it suggests a huge grey area. They aren't what I'd consider advertorials, and it's not the bloggers but the tour organisers who arrange things who get paid. The bloggers will be provided with boilerplate text and links, and it's up to them how they embellish that or whether they nofollow links, but in practice there's a lot of duplicate content going on. Participating blogs also tend to put a positive spin on what they're discussing.
The payment never goes direct to the bloggers, but the pattern would certainly fit JS Harris' description, and for the person paying for the blog tour it doesn't make much odds who gets paid, because the result is very similar to taking out an advertorial.