I've got a client that wants to know if you support Credit Card Data Portability. http://www.portabilitystandard.org/
(You could have a CCDP badge on the foxycart site if you do.)
Essentially the client wants to know if they can get the customers CC's moved to another service (and probably what that would cost). Obviously moving the other customer data is easy with the API.
To avoid their lesser PCI level, data should be moved directly from Foxy to the receiving service provider, for a fee of course (probably charged by at both ends). The link provides some details of how that's done.
From some discussions in the dim past of the forum (like 2009!) - I think you intended to support this but there probably wasn't this buzzword back then.