Since we're talking Fortune 500 here, I'd say it's a virtual certainty that they've employed outside SEO "help".
Even if they have someone in-house whose job is supposedly "search marketing".
These are companies who have entire marketing departments and still hire multiple ad agencies to handle various campaigns. That's the way they've done things for ages, and I can easily imagine the same mindset carrying forward to SEO. This is not a DIY culture we're talking about here.
QUOTE(from the original article)
It was during one such recent excursion that I happened upon the site of an award-winning SEO firm with an impressive list of high-profile clients...
...Of the clients the search marketing firm listed, approximately half were employing "black-hat" SEO techniques.
Of course, as the author is careful to point out, there's no evidence one way or the other who is actually responsible for the hidden text. Could be the SEO firm has been struggling from day one without success to get these companies to remove this crap; could be the companies employ multiple SEO firms and it's others who are causing the problem.
Worrisome, though, is the idea that possibly either the "award-winning" SEO firm did it themselves, or that they have allowed the client companies to get away with it without significant protest, either through apathy or lack of knowledge. Frankly, I gotta wonder just what kinds
of awards this firm has supposedly won, and for what
Speaking personally, if I were in the SEO biz and I knew one of my clients had this sort of stuff on their pages, I'd hesitate before listing them prominently in my portfolio for fear that others would think I was responsible for the crap. At the very least, I'd want to be very clear and specific about the work that I'd done for these firms, so as to discreetly disassociate myself from the hidden text as much as possible.
I mean, if this were some kind of clever legerdemain we're looking at, at least there might be some kind of
bonus points to be gained (in some quarters, at least) by taking credit for it. But we're talking plain old garden-variety hidden-text spam here. The Oldest Trick In The Book™.
And you just know these companies paid top dollar for this "SEO."