Happens in every IT department I've worked in. There are always staff members who see knowledge as power and always managers who allow it to persist.
I have audited my own current IT department (I work in infosec) and have pointed this issue out repeatedly over the past couple of years, it's in almost every report I write but still isn't addressed. They state that since they have sharepoint up and running this isn't a problem, but as always there's bugger all on there from the staff members in question. It's all full of content from the team-minded people, the ones who play well with others etc.
Thing is one staff member in particular has been suspended several times in the past few years for not following change management processes and causing the network to drop, screwing DNS, breaking the web filtering etc. He's one of those who is a full believer in "knowledge is power" and has an inept manager who won't challenge him. I am desperate for that staffer to end up at a disciplinary so I can grill him but until then my hands are tied.
It's bloody frustrating, not just for me but all the IT staff who have to put up with this crap.