This is like Snapchat for the web, except it's too easy to take a screenshot of the content which means there's not much of a point to the view limit.

You could make it difficult perhaps by requiring the user follow a path with their mouse, otherwise white noise appears. That way they cannot actually move their cursor to take a screenshot. Maybe do something else to occupy one of their other hands, such as pressing a series of keys. Of course someone else could be standing there ready to push the "print screen" button or use a camera, like you can with Snapchat. Don't forget a time limit.