How to keep plans for a job change quiet? I am most likely leaving my permanent position at my current university for a permanent position at a new university. I have been given an unofficial offer and we have agreed to terms. I have been told it could take over a month to generate an official offer and contract and that I should not give notice until then. I would prefer not to broadcast the news widely since nothing is set in stone until I am given the contact. Obviously I do not care that much since I am asking here.

In the few days I have known, I have told:


My current department chair since he wrote a reference and my other references
A couple of close colleagues since I valued their opinions
A collaborator in my department since we were beginning to to write a grant together since the move, it is international, would cause major problems
I am now faced with having to turn down a prospective graduate student which would require me to tell at least the head of our graduate admissions committee and maybe the whole committee


I am clearly failing at keeping it quiet. How do you not screw over your colleagues, but still keep the job change quiet until it is official?
This is common in academia. I think you have to be honest with everyone who might rely on you being at your current job in the future, let them know what stage you are at, and ask them to keep it to themselves until you get the official offer. You can only control what you say to others while asking others to respect your privacy in the meantime. 

Suppose that you told everyone in your current department exactly what you have told us, and for some reason your new position falls through at this late date, what's the worst case situation you're worried about? It seems to me that, assuming your current job is held for you, your worst problems will be interpersonal with other faculty that resented your desire to leave. Is that it, or are you worried about some specific ramifications if word got around?