As the article said, you need someone who fits in to the team, someone strong where the rest of you are weak.
Me, I'm kinda dumb (well, I mean, I qualify for mensa, but only just. Meaning, compared to most really good programmers, I'm kindof dumb) But I'm really good at dealing with people who are less socially able, so for me, it makes sense to hire the smartest person I can find, at least for technical positions.
If I were smarter, and/or if I had a harder time getting along with people, or if I was hiring a marketing and/or bizdev guy, hiring down might make a lot of sense.