Only months earlier, public outrage over high electricity bills in the country had brought down a previous government, but Genov saw more reason for anger when the new administration tapped a shadowy media mogul to head the national security service. Furious, Genov posted a Facebook event calling for a protest in Sofia, the nation’s capital, though he was dubious about turnout for a demonstration focused not on pocketbooks but on corruption and cronyism in government.

“We made bets on how many would come. I thought maybe 500,” said Genov, a 44-year-old who helps run a fact-checking website.

But as he arrived in Sofia’s Independence Square, they were streaming in by the thousands, as they have every day since, with the snowballing protests aiming to topple the government.

“We are all linked together, Bulgaria, Turkey, Brazil. We are tweeting in English so we can understand each other, and supporting each other on other social media,” said Iveta Cherneva, a 29-year-old author in Sofia, who was protesting for the first time. “We are fighting for different reasons, but we all want our governments to finally work for us. We are inspiring each other.”

Common bond: discontent

This is the summer of middle-class discontent, particularly in the developing world. From Istanbul to Rio de Janeiro, from Bulgaria to Bosnia, pent-up frustrations of an engaged citizenry are being triggered by a series of seemingly disparate events.

Government development of a park in Turkey has erupted into broad unrest over freedom of expression in a society that, under a devout and increasingly authoritarian leader, is witnessing the encroaching power of Islam. A hike in bus fares in Brazil, meanwhile, has touched off an uproar over official waste, corruption and police brutality. But what do they have in common? One small incident has ignited the fuse in societies that, linked by social media and years of improved living standards across the developing world, are now demanding more from their leaders.

In the Bosnian capital of Sarajevo, thousands of furious residents across ethnic lines united on the streets this month, at one point blockading lawmakers inside parliament for 14 hours to protest government ineptitude in clearing a massive backlog of unregistered newborns. Public anger erupted after a Facebook posting — about a 3-month-old baby whose trip to Germany for a lifesaving transplant had been delayed by the backlog — went viral.

Thousands of ­protesters, including an outpouring of middle-class citizens, are expected in Cairo’s Tahrir Square on Sunday. They return to the touchstone plaza of the Arab Spring in a nation that exchanged a dictator for what many Egyptians now see as a new government unwilling or unable to fix a corrupt bureaucracy and inefficient economy.

Makings of a movement?

On the heels of the Arab Spring, Spain’s “indignados” and the U.S. Occupy movement, some observers see a new class of protest emerging among the global citizenry. If the 1960s were about breaking cultural norms and protesting foreign wars, and the 1990s about railing against globalization, then the 2010s are about a clamor for responsive government, as well as social and economic freedom.

“These are a group of people who are better educated and more connected through technology,” said Robin Niblett, director of Chatham House, the London-based think tank. “In parts of the developing world, this is a new middle class, where the definition of success is not survival. It’s about quality of life, about future opportunity and freedom of expression.”