If you (or your legal representative) think you are able to identify the poster, you should contact the poster directly and request that they remove or modify the posting.

If you believe the poster is someone from your Yahoo! Group, or if you think that Yahoo! hosts the public blog, you should report the incident to Yahoo!.

Yahoo! will review your report under its Terms of Service and take appropriate action. Otherwise you (or your legal representative) will probably have to contact the company hosting the blog to find out whether, under the terms of their service, that company will remove the private communication.

You can report a violation of your privacy on WordPress here: http://wordpress.com/contact-support/
You can report a violation of your privacy on TypePad (MoveableType) here: http://support.sixapart.com/cgi-bin/sixapart.cfg/php/enduser/ask.php?p=tp
You can report a violation of your privacy on Blogger (Blogspot) here: http://help.blogger.com/?page=troubleshooter.cs&problem=&contact_type=main_tos&Submit=Submit