Nope; Apple must have something running in the background listening for incoming connections. FaceTime.app will open with the Accept/Reject box when someone calls.
It really is. I was playing video games a few hours ago, and had my laptop open to read stuff between matches. I got a FaceTime call, and was able to reach over, click accept, and say "Hey Kelly, I'm playing some Halo right now, what's up?"
It was actually a way more pleasant experience than trying to do the same thing on a phone.
