Technological advances and the development of social media have made petitions, public protests and other form of spontaneous activism increasingly common tools for individuals to influence decision makers. To study these phenomena, in this paper we present a theory of petitions and public protests that explores their limits as mechanisms to aggregate information. The key assumption is that, as first suggested by Condorcet , valuable information is dispersed among citizens. Through petitions and protests, citizens can signal their private information to the policy-maker, who can then choose to use it or not. We first show that if citizens' individual signals are not sufficiently precise, information aggregation is impossible, no matter how large is the population of informed citizens, even if the conflict with the policy-maker is small. We then characterize the conditions on conflict and the signal structure that guarantee information aggregation. When these conditions are satisfied, we show that full information aggregation is possible as the population grows to infinity. When they are not satisfied, we show that information aggregation may still be possible if social media are available.