This is brilliant! I love the idea and would be willing to contribute if possible. I agree we don't need another social network where new content is posted. We need a way to sift through the large amount of existing content out there.

My questions:

1) How do you plan on getting content from reddit/twitter/hackernews? Are there api's for this or do you plan to scrape?

2) Would other social sites have issues with you using their content in your social stock market, and possibly profiting from it?

3) Would it be possible for a social network to cut you off and kill your business? For Example: Reddit realized that they are losing traffic because more people are going to [yourSite].com to view Reddit content so they sue you.