Being the new IT guy, I'll try and paint a picture for you about how these knowledge gaps happen, or at least my story.
I attended college at School of Informatics and Computing, with a degree path in "New Media" as they call it. My education consisted of 3-D Animation/Modeling using several programs but with a strong emphasis on Maya. I also took some classes in Web Development (CSS, XHTML). My education stopped there as far as computers go. But I'm comfortable around computers, and I have been ever since I got my first one.
I took a job at a quasi-military academy, working with "at-risk" youth. My first job was simply as Cadre (something like a Drill Sergeant). After about a year, they had an opening for "entry-level" assistant for the MIS department (we're the IT for the organization). I was only TDA'd (Temporary Duty Assignment) initially, but I liked it so much, I decide to interview to keep it and get paid for it. My two years of computer related studies qualified me for the position and I got it.
I honestly came into the job knowing that I knew nothing about most of it, but was confident that I could learn everything I needed. We have a pretty broad range of responsibilities here in my department compared to what I been reading about other IT departments. Some things I do well already, and others I'm working out, but carefully as I do not want to stretch myself too thin.
When I first started, did I know what a Domain Controller was? Not a clue. Active Directory? What's that!? Hell, I even had to learn how to Windows+PauseBreak when my boss told me to add a computer to the network. On the flip side of that, my boss can't code a webpage to save his life. That's where I come in. The rest is time/experience. I feel that knowledge gaps like this aren't as relevant as having the resources to bridge those gaps. I mean, we're supposed to be the best at Googling right? It's in our nature to find solutions. That's the only relevant skill I'm seeing.