The number of cases of defamation by social media is growing. This article examines the principles of assessment of damages as they apply to those cases. In particular, the article examines the concept of the ‘grapevine effect’: a metaphor used to explain the basis for recovery of general damages for defamation. The grapevine effect has been deployed to notable effect in recent cases of publication by social media. The article argues that the role of the ‘grapevine effect’ reflects the purposes of awards of damages for defamation in light of the unique characteristics of social media.