I would like to direct the reader's attention to what Stallman's written about Facebook. I don't agree with a compromise though. Facebook is a net-negative for society. Any interaction with it is harmful. It's really bloody easy to not use it. Have a spine for god's sake! When it comes to changes the software you run on your computer is the easiest of all things to change. If they want to contact you via other channels they will; if they don't they won't.
I'm going to assume Facebook requires an e-mail to register an account. I'm making this assumption to point out that both parties already have a method of communication outside of Facebook's domain.