[zamnos]

> It is very common for someone top of one's trade to command respectable knowledge and skill in another trade.

I don't think that's true. There are some popularized figures, especially ones who have become public figures through music, and then have had continued success, but those are just the pop stars. What about all the doctors or engineers who have found success in one area, and then think that automatically makes them experts in a different area, with disasterous results?