I would say depend on the intention. If someone post a pic of you on the facebook or similar web and that pic is took in their wedding, For sure, that is legal. However, ff someone post your pic on the internet with negative explanation or misleading information against you, that is illegal.

This is very stupid and not funny at all.... You might get in big trouble. Police might knock and warn you, he/she can sue you to court for sure. This is against the privacy act.