Is "Advertorial" a Four-Letter Word? Explains the advertorial concept and has a link to a slow-loading example of an online advertorial for GE. (So you can just guess what the effectiveness is).
The article explains people are using online advertorials to prep and prequalify, then deliver those people into some kind of sales process.
I think the advertorial got replaced by a couple of things. One is articles people post to what I call "article dumps." These, by necesity, take on the layout and look of the hosting site. You have some basic information, then a signature area with a link back to your site. Second are white papers. Not the ones as usually done, but the ones copywriter Bob Bly suggests.
Still, it is hard to believe there are not more advertorials out there.