Jack Goldstone writes in Foreign Affairs about why certain revolutions are successful.

The wave of revolutions sweeping the Middle East bears a striking resemblance to previous political earthquakes. As in Europe in 1848, rising food prices and high unemployment have fueled popular protests from Morocco to Oman. As in Eastern Europe and the Soviet Union in 1989, frustration with closed, corrupt, and unresponsive political systems has led to defections among elites and the fall of once powerful regimes in Tunisia, Egypt, and perhaps Libya. Yet 1848 and 1989 are not the right analogies for this past winter's events.