Here's an interesting legal development for those New Yorkers who chronicle their personal lives on Facebook: A Suffolk County judge presiding over a personal-injury lawsuit has ruled that material posted to online social networks -- even what people post behind privacy settings -- can be used as evidence in court.

That ruling, based on the judge's interpretation of 1986 electronic communications law, would seem to establish a narrow definition of privacy for social-networking users in New York. In California, on the other...