Well I may be in the minority, but I generally use corporate discount codes at hotels around the world for companies I do not work to get a lower discount. I have noticed that most times the corporate discount shows up as a standard corporate rate, and the desk agents have no clue (nor do they care) what company the discount is for.

While I think anyone stupid enough to try and use a marriott employee discount rate at a marriott hotel when they are not employed by marriott should have their rate increased. On the other hand, who cares if someone who works for IBM used a Citibank discount to lower their rate.