A current advertising campaign for Longhorn Steakhouse has people asking an expert various questions. The problem is they are asking questions (usually of a personal or relationship nature) of an expert from a different area (in this case, a steakhouse chef). While it makes for a bit of humor, and a way for the chef to get in a plug for Longhorn, it also points out the trouble with assuming because someone is an expert in all areas just because they are an expert in one.
It should also serve to remind us that just because we may be, or consider ourselves, an expert (master) in a given area we should not presume to be, nor represent ourselves, as an expert in other unrelated areas.
Richard Feynman perhaps said it best:
I believe that a scientist looking at nonscientific problems is just as dumb as the next guy.