By all the references to the word "pirate" and use of the the phrase can't sell Steam games, I can clearly see you people just aren't getting it... I don't wish to sound rude here, but it seems apparent some of you don't understand. In a roughly $6 billion annual retail industry, 1/3 of that is from the used gaming sector. Pirates will always pirate the game that is not what DRM is intended to stop.
Previously when you finished a game you filed it away and maybe came back to again once in a blue moon. Now you take it to your local chain used game store and resell it. A game publisher used to be guaranteed that everyone that wanted to pay for their game would buy it from them. However in an effort to see a return on investments we used to file away, you take that unwanted game to a resale store. Now there is another copy of that game on the market and the publisher is going to make no money on it.
Some may argue but they did make money on the initial purchase... True, however now publishers are competing for business on their own product. This process cuts into the initial sales the publisher would be making, and therefor the final profit on the multi-million dollar invest they made.
I dislike DRM as much as the next gamer, but I understand what publishers are trying to do. This is why I am taking my own steps to battle the the real "pirates" in the industry and refuse to buy or sale used games. Perhaps if we all took this step we could see the disappearance of DRM procedures.