"They ban entire accounts that are not paying" isn't a hard-and-fast rule either; I wouldn't risk anything you can't afford to be cut off from stored monoculture-style in Google's ecosystem, whether or not you're paying, if it's absolutely critical to you. Regardless of whether they apply a different account risk model, the checking thing is experimental and I definitely would recommend against handing it money you can't afford to lose.

Your point on Paypal is valid, and people dealing with Google checking are making a risk calculation like people dealing with Paypal do (but of course, one would hope that over time, the offerings improve; Google entering this market new should be offering something better than Paypal).