[kuzimoto]

I think it would be better to assume that any service you offer could be exploited, than to think otherwise. Lots of places run deals and sales on items with the condition "limit x per person per day" for that exact reason. Or an "unlimited" high-speed phone plan might have a restriction in the fine print where you're throttled after some amount.

Also "expected behavior" seems like it could be pretty subjective. Different cultures have wildly different values.

[IanCal]

It's perfectly fine to assume something will be exploited and call the exploitation unethical.

> Also "expected behavior" seems like it could be pretty subjective. Different cultures have wildly different values.

Sure, and it's down to your expectations. Two people can perform the same act with different intentions, and only one may be unethical.