>The thought of denying a backup worries me.  If the customer's machine
>implodes and when they come for their backup data to rebuild the
>machine they hear "Sorry, your backup never happened because you were
>over quota", I'm just imagining that this would make them far more
>pissed than getting an unexpectedly large bill and having to tell
>their staff to take it easy on the disk usage.

That's pretty much the way that I feel.  An occasional overage occurence
can happen inadvertantly for a variety of reasons, including the first
time through the backups before AMANDA balances the schedule.

There's sort of a || in the NSP world.  A customer might, say, have a
DS3 access link, but have an agreement to only use 10Mb/s of it.
Typically, the provider would monitor the bandwidth used at certain
intervals, and the contract with the customer would state that the
customer would be under 10Mb/s for, say, 95% of the measurment intervals.

If something unexpected happens and a customer exceeds their contractual
level of service once, that warrants a heads-up email message to the
customer, not a refusal of service.  This is simply good customer
relations.  If a customer routinely and substantially exceeds their
contractual level of service, that's a different story.