>USPTO patent examiners will be able to search the site to find prior art they may have missed; the USPTO, complying with the new law, will also provide an online system for submitting prior art. We’re also integrating with Google Patent Search, so every patent application on Google will include a link to discussion on Stack Exchange. Google has also implemented an algorithmic prior art search utility that will be helpful to site participants.

I believe the site isn't so much intended for people trying to find out whether or not their idea is patented as it is for the USPTO to easily find prior art before granting patents.