A closely watched Internet free-speech case is headed to the Virginia Supreme Court this month, with many businesses that live and die by online reviews rooting for the owner of a small, suburban carpet cleaner.

In early 2012, Joe Hadeed, owner of Hadeed Carpet Cleaning Inc., arrived at his office atop a 70,000-square-foot warehouse in Springfield, Va., to discover a critique posted on Yelp.com: "Lots of hype, a mediocre cleaning and a hassle at the end. Don't go with Joe!" wrote a "Mike M." A few days...