You can link your RockBand.com account to your Facebook account to share your Rock Band 3 activity with your Facebook friends. To link your account, log in to RockBand.com and click on My Gameplay, then Settings. Under the Social Network tab, you can click Connect to Facebook. Facebook will ask you to log in with your login information for that site, which will then create the connection to your RockBand.com account.
If at any time you'd like to unlink your social network account, visit this page again and click the unlink buttons.