I generally don't take advice from anyone I wouldn't want to emulate in the area being discussed. So I don't take strength training advice from weak people, I don't take weight loss advice from fat people, I don't take financial advice from poor people, I don't take advice about my personal life from miserable people, and so on.
There are obviously exceptions in the coaching and training arena, but when I'm deciding whether to take someone's advice, there's an unavoidable ad hominem component to the decision -- e.g., "if you know so much, why are you a [pencilneck/lardass/deadbeat/loser]?"