There have been a lot of posts again recently regarding people getting their accounts closed on places like Amazon or Adwords and losing a lot if not all of their income overnight.
So why not "think ahead" and diversify your income sources to avoid serious pain which could be just around the corner?
Just by putting a little extra thought into how you construct your websites you can use many different types of monetization so if you run into issues with one it's not going to be much of a problem - let alone crush your income.
Don't forget to apply the same logic to traffic sources as well, we all know that search traffic can be huge but it's not the only source of visitors.
Diversify now and don't wait for the problems to happen if you might be too reliant on one income or traffic source.