Question for bloggers and t...

So I ran into an interesting dilemma, and my usually analytical brain is having a hard time wrapping my head around it.

Imagine the scenario: I have a blog, a twitter, and a facebook. I'm trying to manage updates to all of them, and I think I've at least determined the rules around how I want to manage those updates:

1. Facebook updates shouldn't automatically update anything else.

2. Blog updates should update twitter and facebook.

3. twitter updates should update facebook.

Now on the face of it, it sounds simple: blog -> twitter -> facebook. However, add in another rule here:

4. Blog updates should go to facebook as a complete entry, not as a bit.ly shortcut.

And now, the crux of the problem. In order to achieve all of the above, I ran into a snag - Blog updates are appearing twice on facebook - the tweet with the bit.ly link, and the facebook pull from the Blog's RSS feed.

5. No duplicate entries on the same system.

This is the one I can't figure out - so I've temporarily disabled the twitter -> facebook link. I figure that currently I don't have that much to tweet, so it's not exactly an issue; on the offchance that I figure out what to use twitter for, it might become an issue again.

So... what do y'all do? Any tricks that I've overlooked?