The quotas should be used to capture revenue from those who regularly exceed a defined level of resources. They should not be used to punish or extort from those who find themselves suddenly very popular, but will (in all likelihood) settle into a normal traffic pattern somewhere on the order of one percent of the spike.
I recognize that many, if not most, other hosting and *aaS providers operate the same way. Still, the second thing I muttered to myself upon encountering the traceback was "Don't host on GAE".
I'll also note that a significant percentage of the upvotes given to this HN listing occurred without having seen the site!