I would say in most cases, being an "expert" is being able to put your money where you mouth is and show positive results while at the same time being able to adjust to any change while still achieving those results.
I didn't know how Google works. I didn't know how Msn works. I didn't know how Yahoo works. But i'm learning something about Information Retrieval, and i've made several tests in my life I never said that i'm an expert ;D but i'm trying to become one. I think that the only way to become a SEO expert is to learn how a SE works. IMHO don't you think so?