Usually the best way to do customer service is to first admit the problem, then solve it. I'm sure not everyone who works at Rackspace is technical, so someone

Usually the best way to do customer service is to first admit the problem, then solve it. I'm sure not everyone who works at Rackspace is technical, so someone could initiate the email notification 5 minutes into the downtime, maybe that could be done via nagios on an external system even. If the system sees that 50% of the servers are down, notify all customers, regardless if you were directly affected or not.