It's never good to ignore your audience, but on the same token it's also generally a bad idea to listen to your audience. Most people have pretty terrible ideas for video games and really have no clue what they want. If developers listened to their audience constantly then pretty much games would suck even more than they do now. The problem is that developers ignore their audience completely, often, rather than trying to find the right balance between discretion and audience input.
Well, actually, the best games are the ones that allow user created content and then publish this content if its impressive or popular enough. Many PC FPS' and some console games use this, so it's not really something they aren't doing. Steam does this all the time. But remember, designing content creation tools is pretty much designing a game within a game, and sometimes that's too time- or resource-consuming. Especially if said tools have to be intuitive enough to be used via an XBox controller. This would also entail building network options into the game as well, not necessarily for MP but for contributing/downloading content. Forge in Halo is p. fun, but it takes way too much effort to design anything legit with the controller.
Copyright laws would make this a nightmare.I mean, it isn't THAT hard to filter out a majority of the junk. How many ideas do devs throw around that are admittedly terrible during the beginning of concept design? I was suggesting that the gamers more do the brainstorming, and the devs pull from the mass of ideas.