In a nutshell the ideas that get most votes on the specific website they have set up receive grant funding. Pretty straight forward.
So what do Pepsi get out of this? Great PR (meant to increase sales), lots of people being driven to their website (meant to increase sales) and lots of people seeing their branding (meant to increase sales).
So how did the company's marketing director judge the campaign's success? "The success has been overwhelming. We have more than doubled our Facebook fans since we started the campaign. We have more than 24,000 Twitter fans".
So lots of new followers via social media but no more cans of Pepsi sold. You do the math.