As things are getting more complex, more people become specialized, and there are a lot more interfaces between specialties that need to be properly defined so things don't break. The more interfaces mean a higher likelihood of a system going wrong. That, and I feel that as long as you have a good big picture, you have a higher fault tolerance because there is a general goal you can identify to strive towards when something does go wrong to correct it. Certainly, I feel that in any field that has become sufficiently complex, there is a practical human limit for a single person to understand the field as a whole. Even if someone can claim to understand a field as a whole in a general sense and how it's major components interact, they will still lose information because of how much they have to abstract.