They are being called the Facebook revolutions, but a better term for the uprisings sweeping through the Middle East might be the Groupon effect. That is because one of the most powerful consequences satellite television and the Internet have had for the protest movements is to help them overcome the problem of collective action, in the same way that Groupon has harnessed the Web for retailers.

“It is a question of co-ordinating people’s beliefs,” said Daron Acemoglu, a professor of economics at the Massachusetts Institute of Technology, who, with Matthew Jackson of Stanford University in California, is working on a paper about the effect of social networks on collective action problems.

Protesting against an authoritarian regime is a prime example of this issue, Mr. Acemoglu said, because opponents of a dictator need to know that their views are widely shared and that a sufficient number of their fellow citizens are willing to join them to make opposition worthwhile.

“I need to know if other people agree with me and are willing to act,” he said. “What really stops people who are oppressed by a regime from protesting is the fear that they will be part of an unsuccessful protest. When you are living in these regimes, you have to be extremely afraid of what happens if you participate and the regime doesn’t change.”

That makes publicly protesting an oppressive regime a classic collective action problem: If everyone who wants regime change takes to the streets, the group will achieve its shared goal. But if too few protest, they will fail and be punished. Even if an overwhelming majority wants change, it is smart for individuals to speak out only if enough compatriots do, too.