For context, here's a rough transcript of the answer Romney gave:
ROMNEY: Do I believe that Social Security should take no part in deficit reduction negotiations? Social security and Medicare are a large part of federal spending. It is about half. Not just this year, but over the coming decades, if we are able to balance our budget, we have to make sure that the promises we make for Social Security and Medicare are promises we can keep. There are a couple ways to do that: one way is to raise taxes on people. Corporations are people. Of course they are -- where do you think it goes? Human beings, my friend. Number one, you can raise taxes. That is not the approach would take.
Update: Romney spokesman Eric Fehrnstrom took to Twitter to defend Romney's quote: "Do folks think corporations are buildings? They're people who incorporate to conduct business. They create jobs and hire more people."
Responding to Fehrnstrom, Jon Huntsman spokesman Tim Miller took a shot at Romney on Twitter, replying "Was American Pad & Paper Company a person/friend?" Romney's firm, Bain Capital, acquired American Pad & Paper in 1992 and closed two of its American plants, laying off 385 workers. It later went bankrupt.