Jeffrey Rosen's headline-writer at The New Republic titled his article "SOPA: A Bad Solution To A Very Real Problem". As you know, I believe that analysis is mistaken. Copyright monopolies create deadweight loss, so a non-zero level of infringement is superior to a zero infringement scenario even if you ignore enforcement costs. But rather than rehash that, let me pick a new fight with Rosen's dubious claim that "There is certainly a price below which authors and journalists won’t produce good work in the first place."
There certainly is such a price, but the price is almost certainly negative. Obviously financial rewards are a factor in people's activity. But in a world in which it was strictly impossible for law professors to earn extra living by offering opinions on newsworthy legal issues, plenty of them would continue to do so. People have strong feelings about things and want to share them with the world! The United States of America in 2011 is, thankfully, not a society of subsistance farmers doing back-breaking physical labor 12 hours a day, 7 days a week. If nobody had a full-time job as a writer, we'd presumably have less writing but not none. This is important not just for copyright policy but for other aspects of society. It happens to be the case that relatively few Americans over the age of 65 are currently avid users of digitial technology. But that will look different 10 or 20 years from now, and I think that retired people using digitial technology to share their passions with the world on a non-market basis will be a potentially important part of the social mix. That could be Wikipedia entries or songs or novels, but I think will probably also include reporting on school board meetings and neighborhood happenings. People have always had hobbies, of course, but it's in the nature of things that building model ships on a hobbyist basis can't have any large-scale impact on the world. Digitial technology becomes an extremely low-cost lever for hobbyist activity to have wide reach, and there's plenty of stuff people will—and are!—willing to do for free.