You go to yoga class and your instructor corrects your form and technigue and then tells you to take this herb or that remedy for back pain. Your trainer instructs you and then watches you perform the exercise and then looks at your weekly food diary and makes suggestions and comments about your diet. We look at these people as experts, but what we should be doing is making sure they are only giving us advise and helping us in their specific field of expertise.
As a trainer my clients ask me questions regarding diet, pain, and just about everything else and it's my job to know where my knowledge starts and ends. I'm not a doctor or a dietician and I constantly have to remind my family, friends and clients that they are better off seeing a professional regarding the specific issue. My dietary knowledge is the food guide pyramid and that's about it. That's why I have fitdiva Jill. I had a client who once used her trainer as a dietician and she gained 10 pounds while following her plan perfectly.
I think my biggest pet peave are those people at the gym who give advise to their friends or even total strangers because they read Muscle and Fitness magazine. Or as we in the trainer world call it, Hustle and Fiction magazine.
There's no shortage of experts these days. A vitamin store clerk can sound very knowledgeable about antioxidants, but he's there to sell vitamins. It's unlikely that he has a degree in nutrition. The bottom line is never take advice without considering the expertise of the person handing it out.