HINT: Many people who add Twitter to their FaceBook Stream end up with unhappy friends.
I did this a number of months ago. What happens is that your Twitter posts automatically get posted to your FB stream and on your friends' page. WIthout my knowledge my friend 'hide' and removed all my posts because they were taking up too much of her screen. If I had not bumped into her in town and spoke in-person, I would never have known.
As a solution I removed the twitter feed.
Another option is to use a third-party program like Tweetdeck and specifically designate which tweets you want posted to FaceBook.
Here are some setting instructions:
Settings / Application Settings
Pull down the Show menu to "Allowed to Post"
Go to Twitter
Click Edit Settings
Application Permissions Tab:
UNCHECK Publish recent activity (one line stories) to my wall