And like always: I'm around to answer questions.
So you may want to consider a way that the discount can be applied on any new services signed up for in the existing cloud panel.
While it's trivial for someone to sign up for a new account, it would make more sense (for your tracking purposes) to have people just enable the discount (once again on additional services) in an existing RS cloud account.
Besides would like to just manage everything from the same account generally.
Actually I'm talking about what you refer to as edge purge (http://www.rackspace.com/blog/cloud-files-cdn-gets-edge-purg...) and AWS refers to as invalidations.
Thanks!