You're not thinking it through far enough.  For one thing, before we can distinguish between the two sample responses you give we need a defined point in time at which the IOU issuer is obliged to give a response at all (a settlement date).

IOUs (taken as meaning any acknowledgement of debt) don't necessarily EVER have to be redeemed.  For example perpetual bonds are never intended to be redeemed - yet are debt.  And on ripple, IOUs can be created for, as an example, shares.  Are those scams because the issuer has no intention of ever redeeming them?

Now IF there were some definition of what minimum liquidity (or maximum time before redemption) had to be provided to be allowed to issue a BTC IOU then we'd be having a very different discussion.  But no such definition exists.  So issuing IOUs with no intention ever to settle is allowed (as opposed to just not prevented) - which is, of course, why noone should grant trust to anyone without making an agreement outside of ripple on the terms for settlement (do even ripple gateways actually provide a guaranteed time-scale for redemption of their IOUs on request?).

Maybe ripple should add a popup when someone tries to extend trust - refusing to do so unless the user ticks a box saying "I have agreed to this issuer's policy on redeeming their IOUs in general and, if applicable, this one in particular".