This seems closely related to the Dunning-Kruger Effect... generally, the more you know about something, the less highly you tend to evaluate yourself, and vice versa. 

I feel like it has a lot to do with the fact that as your expertise in something grows, you also gain a greater understanding of the scope and depth of that area, and consequently, you are better able to assess how impossibly large most areas of study are and how you'll probably never really understand them in as much depth or breadth as you'd like! That makes you feel small - and as a result underestimate your own skill relative to others, being overwhelmed by the scope of the discipline itself.

As an analogy to our understanding of the physical universe, the most advanced scientific thinkers would probably be the first to admit that there is so much that they don't know, and consider their own knowledge to be insignificant compared to the mysteries of the universe,  whereas the ignorant tend to think they have all the answers.

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect