This is a common worry in our field, even for people who are absolutely drop-dead world-class experts in things! You do not have to be absolutely drop-dead world-class expert in things to teach hugely valuable things to people, because the overwhelming majority of people are not experts at $FILL_IN_SUBJECT.
You do server admin? Hypothetical example: Have you ever administered a MySQL server? Have you written a backup strategy for one? Once? Jiggy2011, you know more than I do about a subject which very nearly cost me $$$$ and a heart attack last Thursday. Would I be listening to hear you talk about MySQL backup strategies? Heck yes. I burn with need for that right now. Are there other people who know it better than you? Yes. Do I know who they are? No. I know almost nothing about this field, which includes not knowing the straightforward paths to learning more about this field. You know this subject better than I do, maybe you could tell me who they are, but you can probably also tell me that they're busy building Facebook and since you aren't you're the one actually talking about this stuff.