I see face slapping as a highly effective communication tool between Dominant and submissive. A quick face slap quickly tells the submissive that there is an issue that must be corrected quickly. And unlike spankings which require a high degree of privacy, its much easier if in a public setting to quickly find a discreet spot for a quick face slap. Thus quickly gaining the submissive’s attention to the issue before returning to the public setting. I wish face slapping was brought up more and used more often.