Bending the rules creatively seems to be a popular pastime on FT... but where do you draw the line?

One example case: some time ago, an acquaintance of mine <cough> booked a longish award trip. The tickets came stencilled "BONUS AWARD" and price "0.00"... but, due to the cancellation of the planned flight a few days before departure (thanks Saddam), the flight was rebooked onto another airline and the new tix had no award markings, except for that "0.00" bit. So, after the trip said acquaintance figures "what the hell", and submits the stubs to the FF member service with no additional documentation. Ka-ching, a few weeks later 6000 miles appear in his account! Fair compensation for the reticketing hassle, or unethical cheating?

A few more hypothetical scenarios:

1) I buy a Y ticket, but get bumped to C at check-in. What happens if I send off the C stub? (Flight miles already registered as Y.)

2) I get a cheap round-trip and fly one way only. Is there any way of getting points for the return leg, short of checking in and then no-showing? (And were I to do this, how I can I tip off the airline to not hold the plane for me while not sabotaging my mileage?)