Ethics of not including a contributor as coauthor? Someone (call him Peter) contributed to part of a paper I've written. 
 This occurred over the course of numerous emails (we've never met in person). I am including those results in the paper, and Peter is aware of this.  I asked Peter multiple times to be coauthor but he never responded to that request. I'm ready to submit the paper now. 

(1) Can I submit the paper? I should be able to add Peter as coauthor if he   responds while the paper is being reviewed.

(2) Do I have to submit the paper with Peter's name, or can I submit with a a simple acknowledgement?
The contributor has not meet all the requirements of ICJME (cf. This question of mine) since they have not presumably been part of the writing process. As you have given them the opportunity  (assuming your emails went through) to participate, you have met your ethical requirements. That said, I would pick up the phone and call them and get a verbal confirmation.