For indies I say YES! They are bad.
Heres why:
1. Open Design. Many indies want to create a team. If you design the game all pre-hand its going to make that process harder. Many indies who join teams want a hand in development and design. The game design document says "here is the design, now you help me create it" When teams should be saying " I want to make a game like this, lets bring our designs together and build it".
2. Limitations. Many of the engines out there are very limited in what they can do. If you go and design this feature rich game and go showing off this document many people will have high expectations of the game. Sometimes by no fault of your own you cannot deliver these. Sometimes its better to mold the game around the engine then the other way around. Especially if you are on a $200 budget.
3. Expectations. Muck like above, design documents often start out very thick and full of features and designs. Players and developers both may read this before hand only to have their hopes dropped because of limits, art, money, time, engine, ect... You yourself, the writer may also be swayed from completing the game because of this.
4. Time. Design documents can be very time consuming and that week you spent writing it could have been used more productively on actually creating the game.
5. Design. Sometimes its better to create the game as you go and not be hindered by having to update a document. Sometimes the best ideas come from swift inspiration.
This is just my opinion. Each person is different but I think having a design document as a requirement is a bit over-rated and indies should think about whether they really need one or not.
