Interesting opinion today from the Florida Supreme Court's Judicial Ethics Advisory Committee, which was asked this question in a recent case:

“Whether a judge may add lawyers who may appear before the judge as “friends” on a social networking site, and permit such lawyers to add the judge as their “friend.” 

In other words, can Judge Smith, a judge in the local Springfield civil court, be a Facebook friend of an attorney who practices in Springfield, and occcasionally appears in a case before Judge Smith?

The Florida Supreme Court's Committe said "no".  Doing so would violate certain canons of judicial ethics, particularly the one that states that judges should avoid having connections that make it look like theycould have favoritism.

The opinion is here.