There's no word on whether or not this will be a widely available feature. That likely depends on how the warnings affect habits. It might back away if it notices that many users stop watching, for example.

If this does roll out, however, it could encourage Story creation among those who'd otherwise hesitate to hit the record button. Stories on services like Instagram or Snapchat are alluring in part because you can share moments from your day without leaving a permanent public record. The alert system could discourage creepers from getting around that restriction to take embarrassing screenshots, and could help you spot abuse that you'd otherwise miss.