"With so much competition online these days, it is more important than ever to find a profitable affiliate niche to be successful. A niche is a tightly focused segment of the market. For example, "motorcycles" is not a niche, but "Harley-Davidson motorcycles" could be. And "Harley-Davidson motorcycle accessories" would be an even smaller, or narrower, niche."...... http://become-an-affiliate.blogspot.com/2007/11/how-to-find-profitable-affiliate-niche.html Hope this helps some people.
I do agree. I think that it is just a matter of knowing your market. In the case of your example, It is a good idea to zone in on 1 type of motorcycle like Harley but once you have conquered that you can move on and try and grow bigger.
This is especially the case for beginners, don't aim big, aim small, in the long run it could prove more profitable, then as Magoo 69 said, move on to greater things.
I definitely agree with eventually moving on to bigger things. In my experiences, too many people start big, but get swallowed up quickly. Once a person has more experience then move on to some larger markets.