Here's a cool Mac app that Andreas Lienemann tipped me off about yesterday in the comments to my Pownce Message post.
Moodblast (aka Moodswing) will send a status update to Twitter, Jaiku, and Facebook simultaneously. It will also update status on iChat and Skype as well. And it does some cool tricks with the music you are currently listening to and you can get weather updates as well. I haven't tried anything other than Facebook and Twittter updating, which works perfectly.
Follow this link if you want to download Moodblast and please donate if you end up using it. I did.
Of course, this doesn't really solve my problem of wanting to update Facebook status with Twitter. I do many of my Twitter updates via text on my blackberry and that won't get to Facebook. But if the person who wrote Moodblast can figure out how to update Facebook status automatically surely it can be done by others.