I was thinking switching to full time webmaster last year, but my parents was against it and I'd listen to them. Thank the heavens I did, else I would have been scurrying back to them like I was when I was young. Actually, we earn much more than ever these days since we stopped focusing all of our attention on affiliate networks and individual affiliate programs. It worked wonders. Unless he produced, he earned squat.
Diversity is the key.
The cream has definitely been skimmed off. I run an entertainment site and have not found CPM viable. Most networks will not even look at entertainment sites like mine. Click through rates are just too low. I agree that diversification is the key, but it is becoming increasing difficult to do so.