Claiming authenticity and claiming you have no underlying motive are powerful mainstream marketing techniques. I doubt the motivations of this author are any different than the motivations of the other author that admitted he was trying to manipulate us. This author is just taking advantage of our gullibility whereas the other author was pointing it out. Nobody likes to hear they've been manipulated, but which is really the more valuable message?
There's a reason why TV commercials don't start out with "The purpose of this commercial is to manipulate you into buying this product."
Huh? 37signals and similar do pretty well out of it.
That's an unanswerable question, but you can't rule out the possibility they'd be doing better still.