Facebook connect: Do I need an app id for every domain?

Hey Guys, I'm setting up a commenting system for a group of sites that I have.

With facebook connect, Is there a way for me to avoid getting an app id for every domain I want to use? do commenting systems like socialble.es force you to get an app id?

Sites like Echo and Disqus seem to iframe or 开发者_StackOverflow社区jsonp in tools from their own domain, so I assume they only need an app_id for their own domain.

the answer seems to be that you do.