Russia's hard-nosed approach to foreign energy investors, Ecuador's threatening noises on oil contracts and Iran's reduction of Japan's share in a huge oil project reveal the weakness of multinationals faced with producing countries that want to dictate their own terms.
"There has been a very significant change in the balance of power between international oil companies, and it's clear today that it is the national companies that have the upper hand," said Olivier Appert, president of the French Oil Institute, or IFP.
Examples are legion.
In Russia, Shell is under pressure from the authorities over the Sakhalin oil and gas field, while France's Total is having difficulties with the Khariaga field. Even more ominously for foreign companies, Russia's state-controlled Gazprom has decided to go it alone in exploiting the giant Shtokman field.
Tehran this month slashed a Japanese company's share in developing the Azadegan oil field, Iran's largest onshore oil field.
In Latin America, Venezuelan President Hugo Chavez happily wields the energy weapon, and Bolivian President Evo Morales is applying "nationalization" policies.
"Everywhere there is a return to oil nationalism," said Jean-Marie Chevalier, the director of the energy geopolitics center at Paris-Dauphine university.
Rafael Correa, who has got through to the second round of Ecuador's presidential election, has said he will renegotiate his country's contracts with the big oil companies if he wins.
"Many of them were a hold-up," he said.
"All of Latin America has entered Chavez's dance: Venezuela, Bolivia, Ecuador have all become hyper-sensitive," Chevalier said.
In 1928 the "seven sisters," the top oil multinationals of the time, established oligopolistic control over the price and the production of oil when they met in the Scottish castle of Achnacarry.
But that era has long gone.
"The producing countries must explain to their populations why oil is not bringing in more money, they have to face up to their financial needs and are tempted to milk the cash cow a little more," said Colette Lewiner from the Capgemini Group consultancy.
But the experts point out the limits of this nationalism, noting that the producing countries, guided by short-term vision, risk not investing enough to ensure long-term benefits.
"We have seem that after these phases of oil nationalism, production drops," Chevalier said.
"In Russia, President Vladimir Putin, who is in a pre-election period, wants to show the people that they don't need foreign investment, but that is false," he said, noting the risk that insufficient investment could lead to falling production.