I recently came across the quote by the author Jean Rhys:
“Feed the sea, feed the sea. The little rivers dry up, but the sea continues.”
In the context of internet marketing, this quote directly applies to two things specifically: traffic diversification and niche selection. A lot of affiliates on the web get caught up in the pursuit to find an obscure traffic source that no one else is using and then dominate it. I agree with that mentality, but I disagree if you are not trying to dominate the more mainstream and “sea” like traffic sources such as Google, Yahoo, Facebook, etc.
Next, when selecting small niches to dominate, be aware that yes there are large money making opportunities in small niches (aka a little river). However, be diverse in your selection of niches because during certain times of the year, some are very hot and some are very slow. If you choose a large niche that is always in demand, and thus there is always a lot of money to be made, the little streams of revenue likely won’t dry up.