In a surprising statement, Todd Hollenshead, CEO of id Software had this to say about map modders...

"You know, John Carmack, who is the co-founder of the company and the technical director, he looks to how he got his start in the industry, which he was a hacker and a game fan and got an opportunity to make games. He looks at guys in the mod community not as a threat. Which a lot of companies look at potential piracy, thinking about opening the content of their games and, “what are people going to do?” The fact that they can’t control what the mod community does is very scary to sort of all minds of intellectual property.

But John doesn’t give a s*** about that in all frankness. And sometimes, you know, I’m the CEO and I’m the guy that has to come in and go,”…and here’s the worries.” But given the choice of openness and giving to the community and concerns over restrictions on content, John always errs on the side of openness and I buy into that philosophy as well. I understand the concerns and it causes us some pain and piracy, but at the end of the day I think it is so worth it because there are people who love to play the games, and there are people who also love to work with the tools so that’s just another avenue for them to enjoy the games. And the stuff that they make, people play, and that extends the life of the product. So I think that’s it a great feedback loop.

We’ve benefited from the mod community in a number of ways. Our design lead and our art lead at the company came out of the mod community. They’re in leadership positions at id because we hired them because they were making excellent Doom wad files way way back in the day. That’s how they got their start in the industry. "

It's a very different view that proves ID is ahead of the rest in it's thinking.

Back when the original Doom was published, the WAD's that were generated did indeed extend the life of the game for years, and just about the time that life was expired, here came Doom2.

It's a very interesting article that I would recommend you read since it also goes on to state that as far as Xbox 360 versus PlayStation 3, John Carmack said that he felt that the Xbox 360 was more developer friendly than the PlayStation 3.