My advice to dejan: Most important thing, buy a copy of a book called "Don't make me think" by Steve Krug (http://www.amazon.com/Dont-Make-Me-Think-Usability/dp/032134...). Have it shipped next day. I can't go in to all the reasons you need the book without essentially rewriting the book here but you really, really need it.
On the startup idea itself, I don't see anything inherently wrong with it. I'm not sure how successful the "suggest ideas" side will be only because, in my experience, people tend to be secretive about w hat they feel are their "great ideas". Most people that I've met have a dream of eventually executing on the ideas themselves one day and they don't want to give away a million dollar idea (which is generally their perceived value of it).
The company feedback idea on the other hand is a good one if you can build a community to support it.