Certainly some ideas are different and exciting enough that you wouldn't want to audition them publicly. But for the most part, it's execution that matters. This site seems like a good idea to gauge reaction to those ideas.
How are you planning to get a good volume of user feedback on these ideas? That seems like a pretty big challenge.
Rather than a "yay or nah" style, I'd rather if the feedback were more open ended. Such as: "What do you like about this idea? What don't you like?"