Emily Post would know

I would never answer my cell phone in the bathroom. Even if I was just washing my hands or checking my teeth for spinach, I'm fairly certain that if I answered, the person on the other end would immediately guess where I was based simply on the sound quality of the room.

That being said, what is my responsibility in a public bathroom when someone else decides to answer their phone? Should I cross my legs and wait till they hang up? Or should I just go ahead and do what I came there to do (barring any resulting stage fright on my part) and let the talker worry about the acoustical repercussions?