People who are experts generally have experience or have studied deeply one or more areas. That doesn't generally make them experts about everything even within their own chosen field.
I have 20 years of professional software development experience. I would consider myself an expert in high performance computing with expertise in both threading correctness and high performance I/O. A lot of these experts making recommendations are like me telling you how to design an iPhone app. I have a working knowledge but am far from an expert and may even give you crappy advice.