“PatientsLikeMe managed to block and identify the intruder: it was the Nielsen Company, the New York media-research firm. Nielsen monitors online “buzz” for its clients, including major drug makers. On May 18, PatientsLikeMe sent a cease-and-desist letter to Nielsen and notified its members of the break-in. (Nielsen later said it would no longer break into private forums. “It’s something that we decided is not acceptable,” said Dave Hudson, the head of the Nielsen unit involved.)”