On April 17th, the Orlando Sentinel reported that a Pinellas Circuit Court judge has banned a creditor from posting to her Facebook page, and from communicating with her friends and family through the site. Now, this decision has no value as a legal precedent, but it does suggest how the federal laws intended to protect consumers will be extended to social media.
The article says there are lots more of these cases pending in Florida. It will take one of these cases reaching an appellate court before something really important is established.
Nothing prevents lawyers from trolling your public pages for evidence and potential witnesses, of course.