I luckily never got my account suspended, but I've certainly done some minor violations of the TOS here and there (e.g. in college I downloaded a few copyrighted books and stored them in my Drive for my strictly personal consumption, and I'm sure those files could be fingerprinted and detected by Google, ...).

From what I've heard, when it happens it's not quite easy to regain access, in the best case it takes many days, and the frustrating thing is that there's no support to which you can appeal to, you're mostly left to yourself (e.g. Google employees connections, twitter noise, ...).

I find it silly that my electronic identity would be held hostage in such cases, so with an external domain I can flip a switch and keep receiving my email somewhere else.