Knowledge can be "deep" or "wide."
"Deep" means you know everything there possibly is to know about a specific topic. People consider you an authoritative expert on wine, or haikus, or the Beatles. (Tip of the pen to B.)
"Wide" means you have trivial scraps of knowledge in many different areas, but not the comprehensive information of the expert in any single discipline. You might know the 54th element on the periodic table happens to be Xenon, but you have no idea how many elements there are in the entire periodic table. In the old days, we called these people Renaissance men/women.
As I'm sure you've deduced from the title of this entry, my knowledge tends to be "wide" rather than "deep." What can I say-- I have a degree in the liberal arts tradition. The funny thing is some people witness my recall of a peculiar info tidbit (e.g. using HTML comments to "cloak" Javascript so it can pass through a validator successfully) and assume I'm an expert at that topic. It's even funnier when someone with "wide" knowledge (mistakenly??) believes they are an expert on a topic.
I have a friend, the "Agoraphobe," who considers herself a Beatles expert. One day, she meets this guy who also has a passionate love for the Beatles. She takes a passing fancy to said gent and strikes up a conversation. During the course of the conversation, the question comes up "Who is your favorite Beatle?" The gent answers: "Peter." At which point my friend assumes that said gent is a poser, and we all know that experts and fanatics cannot possibly tolerate faux fans-- so she dismissed said gent from the possibly interesting queue.
Later, when she is recalling her triumphant exposure of said poser to me, I stop her and ask, "Wasn't the drummer before Ringo named Peter something?!" "Yes, Peter Best," she replies, and then after a long pause: "You don't think he really meant . . . aw, [expletive], you've got to be kidding me!"
Is there some lesson to be learned there? Beats me. With terminology like "wide" and "deep," it's tempting to finish this entry off with a witty double entendre. Except I can't help but think experts are missing out on some friendships/relationships/opportunities because of their elitism-- and if renaissance people could just focus a little longer on one subject they might be taken a little more seriously than "dilettantes" or "jacks/jills of all trades."
There is no ancient guru on the mountain top who knows everything. He vanished to make room for modern conveniences like radio towers and cell phone antennae. We are our own experts; we are our own renaissance men. Everyone has something to offer, and we need to wake up and realize it soon.