www.bigthink.com seems, honestly, like one of the most brilliant ideas I've seen for some time. (I won't pretend this is saying much, I'm seventeen) The problem with it, as stated elsewhere, is that eventually it will attract not only big thinkers, but those who would openly mock the ideas of others, because they disagree. (There are also minor technical issues with the site, but it is in beta, and it wouldn't seem productive to discuss those here)