You are mostly correct. We are primarily regulating access to a all@university mailing list, but we also have restrictions that prevent mass emails being sent via gmail (though I'm not the authority on this). You are correct, nothing prevents a compromised account, that I know of, from sending out emails one at a time to an list of users, though we do have control over all email accounts and can disable a compromised accounts. If the traffic is internal we have other ways of preventing it. I'm not saying our solution is an absolute substitute for all combinations of possibilities. Just that if we were to be blocked we'd have to deal with it in some other way then to disable google forms. We just couldn't get away with it, and according to some of the comments, Oxford couldn't get away with it very long either.