Not quite. While the overall extent of shaping is determined by network constraints, individual accounts are supposed to have shaping applied more or less aggressively based on their recent usage. At least, that's the way it was originally explained to us. Unless something has changed, what is supposed to happen is that if they have to, for example, shape everyone to 50%, an account with not much recent usage might be only shaped to 75%, while higher usage will be shaped to 25%, to average out at the desired level. Having said that, though, I think the system is completely broken, because if 9GB of usage and 1Gb in a week gets you any kind of shaping there is something seriously borked.