The more I think about the security of Google Cloud.
the more I am convinced it's more secure than traditional systems.
Take a look at Sony Pictures hack, it propagated by idiot users emailing files around, giving passwords to other people and so forth. It was a house of cards. Pretty much every company works like this (sadly).
Take a full cloud solution where email, documents are all done in the cloud. No longer do you send files around (it might look like it to end users), it's sending links to files under the covers. Until it's taken from the cloud, it only lives in one place. Delete it, it's gone everywhere. You sack Johnny, and close his account, so goes it access to the file.
Combine this with enforced group poilicy 2 factor authentication, so you know who is supposed to be accessing things, is, and you have a far more secure setup than you have in the current wild west of Windows, Microsoft Office and USB sticks and 2 gazillion copies of the same file in everyone's inbox...