Problem: 'Add everyone in my org' is enabled for anyone who has access to create powerapps. When sharing an app, anyone can very easily send an invitation to everyone in the company which is in my case is over 30,000 users. This has been considered to be such a risk that PowerApps has been switched off completely company wide until this is resolved.
Suggestion: Allow an administrator to switch on the 'Add everyone in my org' and the 'Send an email Invitation' features. If any app is deployed to a large number of users, this will be done through groups.