The Legal Ethics Committee of the District of Columbia Bar has just issued two opinions on social media use. Ethics Opinion 370 is available here. Ethics Opinion 371 is available here. The Legal Profession blog has a summary here.
Opinion 370, does not seem to add anything new. It concludes that "a lawyer who chooses to
maintain a presence on social media, for personal or professional
reasons, must take affirmative steps to remain competent regarding the
technology being used and to ensure compliance with the applicable Rules
of Professional Conduct."
Opinion 371, on the other hand, provides more information and analysis in an attempt to provide guidance about "advice and conduct by lawyers
related to social media in the provision of legal services, including
whether certain advice and conduct are required, permitted, or
prohibited by the Rules."