I really believe that ideas are literally valueless. They are important because when you look at the idea you know what shape the game will be, but without implementing the game logic and testing it and tweaking it and munging it and creating art (and an engine) that dresses it well and makes it viscerally appealing and and and... you're left with something so far removed from being an actual game that thinking of it as one is more an act of flagellation than real designing.

The job of a designer is less to have ideas, and more to refine ideas, and even more to reject ideas that don't work, and in my experience those are rare skills. I too have a host of ideas for games that I am enamored with, but the reality is not that they would make great games, the reality is that they might be made into great games.

So should you care even if someone does steal your idea? No. If you're a good designer they can't steal that anyway.

Plus there's always the hope that your idea will be stolen by some great people and that they'll make it into a great game, that way you get the best outcome: No work and you still get to play the game of your dreams.

So to address the question: In this forum, people will occasionally post ideas. Sure someone might steal the idea, but the theif'll have as much work to do with it as you will so you shouldn't care about that. What the forum is for is to help you work your idea into something good.

Iopenka, if you're still following this, don't post your whole idea and ask for comments, not because someone will steal it but because, like hackers, designers don't want to do all your work, but they're happy to help with interesting questions. Start making your game, when you run into a design quandary, post that and you'll get some really helpful answers, and you'll be glad you did it.