This has come up several times...you get an offer and don't tell anyone until you have it "in writing". What do YOU mean by this? An email with some details? A formal contract? I can just see the formal contract taking a long time to arrange and I'd hate to hold off telling my current institution any longer than necessary (this is hypothetical for me at the moment).
<<What's up with spell check?>>
Well, I had a letter faxed from the Dean with all the details of the *offer* made orally by chair A. Later, when I was waiting for the contract all my friends were signing for their systems...I find out that mine is in a state that doesn't give contracts at all. Then, in May I got a strange short letter from the President of the U appointing me for the next year. Turns out that *this* letter was the only real "committment" of the system in that state. No one ever mentioned this to me. Technically I wasn't "offered" a job in this state without that last two line letter. Glad I didn't know that then
So, yes, I'd love to know what the committment threshold usually is. Because now I feel i need to know state law to determine if I have an offer or not that I should act upon!