I like your idea. However, I don't like the fact that simply by submitting something I automatically grant you a license to do whatever you want with it. In fact, I was going to submit a short story but will not after reading your terms and conditions.

I think that to make the site successful you need high quality stories that people want to read and vote up. I am not sure that authors would be willing to post on your site knowing that they are then granting you a license for their work.