If you haven't read The Cuckoo's Egg, I'd highly recommend it. It details his experience tracking down one of the first "hackers" back in the 80's, when he was a sysadmin for Lawrence Berkeley National Laboratory.
I'd say that it's one of my two favorite non-fiction books (the other being "Surely You're Joking Mr. Feynman").
The last time I've been so passionate about something was when I was around 10 or 12. Since then I've trained myself to be (and act) not so passionate anymore, because it'll make you look like a weirdo to most people. However, it brought me to a point where it's hard for me to get excited about anything at all, not to speak of expressing it properly...
This same phenomenon happened to me not long ago actually, when I discovered that two of my all-time favorite bands shared a guitarist (Greg Edwards of Failure and Autolux). Is there a term for discovering that two people you know of are actually one and the same? I find it to be a rare pleasure-- you can almost feel the mental connections linking themselves together, and afterwards the world feels like a smaller, more logical place.