All very relevant. It is interesting to note that the few people who did make money in the gold rush did so by running pretty much traditional businesses: even gold rushers needed to eat, live somewhere, use basic tools etc. The same pattern repeated here in South Africa during both the gold and the diamond rushes.
My uncle was an artist, and he always held that artists should at all costs resist running after fads. In his day, galleries would put tremendous pressure on artists to paint in this style, or that subject matter, because it happened to be popular and thus made them good money. But soon the fad would be over and the galleries would simply move on to the next artist to exploit in this manner.
My uncle steadfastly stuck to his own style and way of work, and instead of making a fortune in a small amount of time and then fading from the scene, he built himself a career and eventually became quite wealthy. I suspect the same principle holds true for all or most careers.