Buying used is covered by what's known as the first sale doctrine. If the item is a legitimate product legitimately acquired, the law states that the purchaser has rights of resale on that physical copy. This is why you shouldn't be so gung-ho about the all-digital-download future, kids. The first sale doctrine is clear only when there is a physical object involved.
http://en.wikipedia.org/wiki/First_sale_doctrine
Buying used does not remove money from the developers. For it to be used, it had to be PURCHASED the first time. Which means money went to the developers. The people who buy used are stating, in the market, that they will tolerate the defects and perils of a used market to capture value. If developers don't like that, they need to investigate legitimate economic means to counter it, like lowering prices or increasing production runs. For some, this can and will never happen. The same situation exists for painters who see (if they are lucky to still be alive) their work passed on for many multiples of what they may (if they are lucky) have charged for the initial sale. And sculptors. And car manufacturers. Basically, anyone who produced a solid good for sale. I have zero sympathy for someone crying about physical reality.
Piracy, on the other hand, violates just about every portion of the first sale doctrine by transferring ownership of non-legitimate goods. The format of the goods makes no difference to this argument. I have zero sympathy for pirate's justifications for what they do. They all sound exactly like the rationalizations of every petty criminal, ever.
I have more to say, but I'll stop here to remain on topic.