Earlier this month a federal magistrate judge in Virginia held that placing privileged materials on an unprotected file-sharing site waived a plaintiff's attorney-client privilege and work product protection for those materials. The case is called (also here). For more details, go to 33 Law. Man. Prof. Conduct 76. The ABA Journal has more information here.
Although some jurisdictions are divided on the issue of whether accidental disclosure automatically waives the privilege, in this case the judge held that the party's actions "were the cyber world
equivalent of leaving its claims file on a bench in the public square
and telling its counsel where they could find it. It is hard to imagine
an act that would be more contrary to protecting the confidentiality of
information than to post that information to the world wide web."