In order to get this to work, you need to set up the Selective Twitter Status application up on Facebook.
Three StepsAny tweets you post that end with #fb will now update your Facebook status.
Step 1:
Go to the Selective Twitter Status application page on Facebook.
Step 2:
Enter your twitter username.
Step 3:
Press Save.
Selective Twitter Status - Help Page:
The hashtag should be added to the end of your tweet.Follow the developer on twitter @andyy
One exception: it's ok if the #fb is followed by a space and then a link, e.g. "This is my tweet #fb http://linky.com/linky". This ensures it will still work with apps that automatically add links e.g. TwitPic
There must be a space before the hashtag.
Follow me on twitter
Follow me on facebook