It is unethical, and I vaguely agree about crediting, but I am of the opinion that if it was really "property" you didn't wish to be copied you wouldn't make it copy-able in the first place, or you would distribute it only to people you trust to not copy. If it's property, it should be protect-able. 

If someone CAN Ctrl + C they will, crying about how it's mine and you can't, is just kindergarten arguments at that point.