This would just create a new market for art paparazzis who would find any and all means to inflitrate such private viewings with futuristic miniature cameras and other sensors and selling it for a premium. Less than 24 hours later the files end up on hundreds or thousands of centralized and decentralized servers.
I'm not defending it. Just acknowledging the reality. The next TMZ for private art gatherings is percolating in someone's garage at the moment.