Turns out a court of law isn't the only place where what you say can be used against you. According to this piece from, insurance companies can look at what you write on blogs, online forums, and other social networking sites as part of determining whether to give you coverage. From the piece:
Your online writings could be used in a determination made for or against approval of coverage of your treatment...
We love and enjoy the empowerment that online social networks have brought so many people. But we are also painfully aware of just how public the information we make available to them becomes. And, once indexed by a search engine, how virtually impossible it is to thereafter remove such information from the Internet.
Protecting the privacy of your health information online is basically a matter of applying common sense: post online anonymously or using a pseudonym; use private forums when you post about your health (mailing lists, a blog restricted to those you give access to); and so on.