Management - We all understand that there are BIG benefits to free trade

Management

All right, this week's discussion in an important one.  We all understand that there are BIG benefits to free trade (we can think of the benefits outright, or we can think of the costs of protectionism).  Having said that, the government often intervenes in the global economic environment.  

Based on what you've read in chapter 13, what are some justifications of government intervention?  In your answer, please make sure to at least touch on public goods, monopoly power, externalities, etc.  Define key concepts as you go...  As we progress throughout the week, explore with your peers how can we use what we know about how/why the free market works to make government intervention more efficient?