In order to be worth his salt, a Game Designer has to be able to demonstrate that his input on the project is going to result in a sufficiently better product to compensate for whatever sacrifices the team must make to include him - and by sacrifices, I don't just mean money. Creative input tends to be important to everyone on the team, doubly so if they are doing it on an unpaid basis. For that reason alone, no Game Designer can afford to be some kind of creatively monopolistic Ideas Guy - rather, he takes creative input from the entire team, fills in any gaps with his own ideas and collates it into something coherent and fun.
Fun is the key of course - that's the where the value of the Game Designer ultimately comes from. Not from his ability to write colossal design bibles that nobody reads. Not even in his ability to have Cool New ideas for Awesome New Features. The skill of the Game Designer is in his ability to identify gameplay issues, fix or even cut features that don't work, add features that do work, and create gameplay that is engaging for the target audience.
Ultimately, as I think several people in this thread have already said, indie Game Designers are respected - once they have proven themselves. But then we're back in the same sort of chicken and egg situation that wannabe Game Designers face everywhere - you can't prove yourself unless someone will take you on, and no-one will take you on until you've proven yourself.
As a game designer, how do I get my foot in the door then? The view within a lot of indie teams seems to be that you must be able to contribute within some other role. But then there are others saying things (even within this thread) which negate this way of thinking;
"Everyone can be a designer, not everyone can be a programmer." - This is a fallacy. Everyone can have an idea, but not everyone can be a designer. This comes down to the difference between an "Ideas Guy" and a "Designer" again. I think it's safe to say that everyone involved in the production of games has their own idea for a game. That doesn't mean they have a workable design for a game, or even the ability to turn their idea in to one. Having "an idea for a game where you build and run a city" doesn't mean you could design SimCity or CitiesXL.
"Programmers have spent years learning to program, designers haven't." - This may be true. But not always. It is probable that a lot of designers have not spent years "learning to be a game designer" that doesn't mean they have not spent years learning to be a game designer. Programming, modelling, artwork, are all more discrete tasks so they're easier to define - "I have been programming for 10 years" - a game designer is as creative a role as a game artist, you do not wake up one day, decide to be a game designer, and have the prerequisite skillset. You have to be a writer, a salesman, a businessman, and a lot of other ill-defined things to be a successful game designer, and just like everything else (unless you're some sort of genius) you have to spend time learning to do all of these.
"Game designing is not a fulltime job" - True or false. Depends on your circumstances. In an indie team, I would say that it is less true than in a AAA studio. A game design team will spend months on the design fulltime, before handing it off to be built, with some corrective processes here and there. People in this thread have been saying that if I want to be a game designer for an indie team, I should turn up with no idea at all, and work on the team's idea. This means a lot of iterations and rework (unless you can prevent production from starting for a few months while the design is worked on). This isn't a part-time job. If you have a designer that can turn up and hand you a document and you think he's getting off easy and working part time, then you should be happy because a lot of time has gone in to that document that you are apparently unaware of.
You're welcome to do differently in your own projects, and you can disagree till you're blue in the face, but in the real world that's just the way things are -- and if you take some time to research professional design you'll find hundreds upon hundreds of supporting examples, such as the one I linked above where Quake changed from a fantasy RPG to a sci-fi FPS during development.
So, taking the quake example. If I, as a designer, had written up my GDD, handed it to the development team and left it at that (since I, as a designer, am really unecessary) you would have created a mediocre RPG rather than the one where I stayed on through all the reiterations and redesigns, and created quake.
A GDD is only a starting point. There are hundreds of examples sure where a design has been vastly different from the final product, but I'm sure you'll find thousands of examples where the Game design has not been. Within these you'll see trends whereupon a bad design document makes a bad game, a good design document makes a good game.
A good game takes good design. Whether this happens before or during production. Whether this is done by one "game designer" or the collaborative team, you still need good design. Working with a good game designer who can dedicate most (if not all) their time to the game design can make the production a lot easier, and make a better game, but (for indie teams) it is a lot harder to prove your worth as just a designer.