It depends on your operational security, your understanding of the sharing model, and your understanding of the terms of service.
If you sign onto your Google account with 2-factor authentication, and you understand what you’re doing when you share a doc with others, it’s extremely safe.
By “extremely safe,” I mean that I am, myself, considerably more concerned about the possibility that someone could break into my house and steal my desktop computer than I am that anyone would be able to get access to information I keep on Google without my consent.
If you don’t use two-factor authentication, someone phishing you for your password can get access to your account. If you have 2FA setup, someone needs access to both your password and your phone to get into your account. (You lock your phone, right?) So do that. Do that right now if you haven’t. (
Sign in - Google Accounts).
Print out the backup codes too, so that you can get into your account if you ever lose your phone.
If you accidentally share a document with the whole internet and then post the link to it somewhere that other people can find it, everyone will be able to read it. So don’t do that, or if you do, make sure it’s really what you want to do.
The other major risk associated with using a Google account is doing something that would cause you to lose access to the account. Forgetting your username, for instance. Or using your Google account to do something that violates the terms of service, like spamming people or distributing pirated movies. (Anyone using a Google account should read the
Google Terms of Service.)
It can be very difficult and time-consuming to recover access to your docs if you lose access to your account. Take this risk seriously. Keep a copy of your access credentials somewhere safe. Print out the backup codes and keep them safe. Don’t violate the terms of service.
That’s where all the risks are, and that’s what I worry about. I don’t worry about someone breaking into Google and stealing my data. Not in the least.