<<as credit card companies do make money from areas besides interchange fees (late fees, overlimit fees, near-usurious interest) and having an annual limit on rewards limits their exposure >>

Granted, but to the extent that rewards are tied exclusively to charge volume the issuer cannot be assured of generating any fee or interest income, especially on charge cards, although American Express does keep asking if I would like to finance anything at prime plus 9.9% . I do realize there have been rewards tied to carrying a balance, but I don't think these are the programs discussed on Flyertalk.

dennis