One important difference between written and spoken language is that in the former case readers have the luxury of looking words up in a dictionary if they don't know them. When speaking, I'm careful to avoid words I suspect might not be understood by my listeners, but when writing [1] I generally use the most precise word I can think of, even if I expect some readers won't know it. (Indeed, for particularly tricky words I'll often link the dictionary definition myself.)

[1]: Examples include http://railstutorial.org/book, http://tauday.com/tau-manifesto, and http://learnenough.com/command-line-tutorial