I get obsessive about certain things like keeping my money in denominational order in my wallet, but I also keep myself walled off in the network...for example, I work in a network that is 99% Windows, but I manage to use Ubuntu on my workstation with a virtualized Windows VM for those times when I have to interact with Active Directory (or I use the terminal server to access it). I keep my passwords separate, using the AD login just for email.
Basically I obsess about basic security of my system; I have to turn some control of things to other people, but my own workstation doesn't use Windows security so a student would have to hack my specific workstation to get into it. I have separate passwords for certain things that I have more responsibility for; i.e., I primarily administrate the VMWare setup we're testing out, so it has a password that is separate from other accounts. An internal bulletin board system has a separate password from other things.
That way I keep a little "walled garden" while if one password is cracked the attacker doesn't get carte blanche with everything.
I have lots of such quirks though; like obsessed with avoiding people who chew with their mouths open, and certain noises drive me nuts so I don't mind staying in the server room where there's a lot of white noise to drown out other sounds.
Did I mention I'm diagnosed as having Asperger's?
Oh, and I think Joel Spolsky mentioned on a podcast that the Asperger's personality traits are common among technology people, because he and Jeff were discussing a question posed to them about programmers that are "difficult to get along with" in teams. Joel talked about how for them it's often best to just tell them that so-and-so isn't comfortable with said programmer staring at his shoes when talking to them, and the tendency for that personality type is to thank the person for bringing it to their attention; we usually don't get offended by what other people would see as a social faux pas.