Right now it's just an enumeration, used by the customer models as simple labels but not used elsewhere in the server. It's hard to see how these labels have sematic value, because they do not clearly correlate with usage profiles or subscription behaviors or anything else that might be useful.
Issue #468 suggests that we simply eliminate the CustomerType type. It would eliminate a small amount of code, but more importantly it seems to me that it would reduce a potential source of confusion.
If you think we should NOT eliminate CustomerType, please add your comments directly on the issue, rather than through the mailing list, within the next two days. If I don't see any strong counter-argument by then, I will be sorely tempted to rip it out.