But why?!??! Why would you want them to do any of that.
Of course Google could add more 'secuirty' controls on top of the sharing feature. They could require a password, or passphrase, or make the link one-time use only, or only available to Google accounts.... But for every extra control they add, thousands of users would get frustrated and essentially be shut out from the feature. Somebody's grandfather wouldn't be able to open pictures of their grandkids, somebody's aunt would get frustrated sharing pictures of her cooking.
Security is like marketing in that it can be a big black hole that you can dump more and more resources into with no benefit. There is a very real cost to security.
Of course Google could add more 'secuirty' controls on top of the sharing feature. They could require a password, or passphrase, or make the link one-time use only, or only available to Google accounts.... But for every extra control they add, thousands of users would get frustrated and essentially be shut out from the feature. Somebody's grandfather wouldn't be able to open pictures of their grandkids, somebody's aunt would get frustrated sharing pictures of her cooking.
Security is like marketing in that it can be a big black hole that you can dump more and more resources into with no benefit. There is a very real cost to security.