Do you encrypt your text messages? The recent demonstrations in Egypt, which overthrew the government, relied heavily on cell phones, and especially texting, to coordinate the massive rallies. It was suspected, and later admitted, that the secret police had already set up a monitoring system for text messages. The cell phone companies would only admit that there were certain "national security measures" that they could not comment on. So before the 18 days of demonstrations were over, apps were released for encrypted text messaging (on Android phones).
However, encryption is not perfect protection. Just using encryption enables the police to identify who is doing so, and which type of encryption you are using. If only a few people in the country are using a certain type of encryption, you are suddenly a "person of interest" for the secret police. But if there is widespread unrest, and lots of people are encrypting their text messages, the cops are screwed. But only if the revolution succeeds. If the dictator stays in power, the government has the time and resources to study those cell phone records thoroughly.
Terrorists and criminals also use these encryption tools, but that just draws attention to them. Some nations have the resources to break, after a few hours or days, these encryption systems. But any police force that can monitor the cell phone traffic, can notice the pattern of calls made by people with a particular type of encryption. So these systems not only help large groups of demonstrators, but are of limited use for terrorists and other criminals.