TR: How have you been led to some of the problems you've worked on recently? What's been the source of some of your questions?

JC: For me personally, having been at a company this past decade rather than having remained in academia meant that I got to hear about some problems much more quickly than I would have otherwise. I got to take some of these exciting things that were happening in the real world and be one of the first people to model it, because I was hearing about it. Then I could take those problems out into the mathematics community and get other people working on them. For example, I heard about link spam really early in the game, and how it affects the quality of search-engine results. Also, I hear everyone talking about social networks at a different level than if I were at the university. I'm convinced that people who study graphical systems and networks at universities are all going to be looking at recommendation systems three or four years from now. But I got to look at them a bit earlier, because people around me were asking, "How would we monetize a social network?"

TR: You've studied that problem with your work on recommendation systems. But recently, Facebook, for example, has struggled with some of its efforts to monetize. Its Beacon advertising system suffered from this tension between sharing information through a network and protecting the privacy of members of the network. What can be done about this?

JC: Those are exactly the kinds of questions that we're asking. We've looked at how to design systems that have various properties. We might come up with a theorem saying you can't have a recommendation system that will deliver all the information you want and have all the privacy. But then you could say, "Okay, which properties am I willing to give up, and which kinds of recommendation systems will have the kinds of properties that I want?" We want to work with sociologists, psychologists, and economists in our new lab partly because I'm a mathematician and can model these kinds of things. I can get a mathematical formulation of various forms of privacy, but I might not be able to tell you what the majority of people want, or what people in a certain age group want. So if I work with sociologists and psychologists, they can suggest to me various different kinds of properties and order those properties for me. Then I can come up with a mathematical framework and say, "Here is an algorithm that will give you a recommendation that has the maximum number of properties in that ranked order." With all the data that we've got and the kinds of things that we want to do, I think it's really time for mathematicians and computer scientists to start interacting with sociologists and psychologists. I'm not an expert in what people want. I can just model what people want.

TR: Will this sort of thinking guide your approach in the new lab?

JC: I'm hoping that our new lab in Cambridge will be the perfect environment in which to look at these kinds of questions. We're going to try to bring together all the right people.