The House Committee on Energy and Commerce is investigating alleged withholding of clinical trial data in a pharmaceutical trial. Anonymous posts on the CafePharma.com site suggest that posters knew about the trial results months before they were publicly released, so the House Committee on Energy and Commerce asked CafePharma for "all records relating to any posting on CafePharma.com related to the ENHANCE study, including but not limited to ... e-mail and internet protocal addresses of anyone creating such a post." (This was indeed just a letter requesting this, not a subpoena, but I take it that there was an implicit threat of a possible subpoena, and the letter speaks of the possibility that the Committee would "require" more information.)
[W]e do not collect any user information with anonymous posts (including IP addresses). Therefore, we do not believe we will have any information to provide regarding these posts.