At least one media outlet in Cleveland is reporting that a paralegal has been dimissed from a murder case because of her Facebook Friends List which included the county prosecutor and other high level officials in the prosecutor's office. Interestingly, it was the prosecution who informed the court about the juror's Facebook Friends List. When this information was initially revealed the defense requested a mistrial but the trial judge decided to just replace the juror and start deliberations over from scratch.
I presume that the juror's Facebook page was private, which is why the defense did not discover the Friends List. If it was available to the public and the defense failed to review the page then the defendant (if convicted) would have had a decent ineffective assistance of counsel claim, especially in light of the fact that this defendant might face the death penalty. Investigating jurors online is increasingly becoming the norm for many attorneys.