There's an interesting commentary in the Las Vegas Review-Journal by its Editor, Thomas Mitchell. The situation he describes represents the intersection of free speech and a site's privacy policies and arose when the journal published an article about a federal tax evasion trial:

The story was posted on our Web site. When last I checked nearly 100 comments were appended to it, running the gamut from the lucid to the ludicrous.

This past week the newspaper was served with a grand jury subpoena from the U.S. attorney's office demanding that we turn over all records pertaining to those postings, including "full name, date of birth, physical address, gender, ZIP code, password prompts, security questions, telephone numbers and other identifiers … the IP address," et (kitchen sink) cetera.

[…]

Bottom line: We could fight the federal subpoena, at considerable expense, and lose. Our attorneys are now trying to see if we can limit the scope of the information sought.

What the prosecutors don't appear to understand is that we don't have most of what they are seeking. We don't require registration. A person could use a fictitious name and e-mail address, and most do. We have no addresses or phone numbers.

To add prior restraint to the chilling effect of the sweeping subpoena, we were warned: "You have no obligation of secrecy concerning this subpoena; however, any such disclosure could obstruct and impede an ongoing criminal investigation. …"

This situation is another reminder about the importance of sites' privacy policies and data retention practices. They can't get what you don't have.