That debate is starting to play out in the court system, where a small but growing number of lawsuits have been filed against Twitter users by those claiming to have been libeled or defamed by so-called “tweets” — the 140-character messages that users send to their followers.

Twitter advocates won an early victory last week when a Cook Country, Ill., circuit judge dismissed a defamation suit filed by a Chicago-area real estate management company against a former tenant who tweeted about mold in her apartment. News of the suit went viral on blogs and Twitter as social media users considered the potential ramifications.