So, I edited this down a lot and left out parts that are obvious oligopolies like the media, but left out sectors that are also interesting, like half the publishing industry is controlled by 2 corporations, also it's a couple years old. If you want to fact check them just google the text.

In oil and gas, 4 companies control a little over half of all the oil reserves in the world (Saudi Aramco, National Iranian Oil Company, Qatar Petroleum, Iraq National Oil Company.) Although these are state-run, publicly traded oil and gas companies consist of just a handful of players as well. Meaning, the most vital resource to our societies is controlled by a handful of corporations and/or dictators. In the 2006 American election cycle, $19 million was spent on political donations; most of it going to republicans wherein cutting or abolishing the E.P.A is a regular talking point. Under the Bush administration, Exxon had been consulted on climate change negotiations during talks about the Kyoto Protocol. As the U.S. withdrew its operation in Iraq, the Wall Street Journal ran a story with the self-evident title, "U.S. energy firms move into Iraq as troops leave".

A study from the American Medical Association done in 2007 on competition among healthcare insurers found that,

"'the two largest health insurers, Aetna and United, had a total membership of 32 million lives. As a result of mergers and acquisitions since 2000, the top two insurers today, WellPoint and United, each have memberships, respectively, of 34 million and 33 million, totaling more than 67 million covered lives. Together, WellPoint and United control 36 percent of the national market for commercial health insurance. In 2004 and 2005, 28 mergers valued at a total of $53.8 billion were completed or announced'"

Their study finds that, state by state, virtually two insurers control the market. In Alabama, Blue Cross Blue Shield controls 83% of the market. In Rhode Island, it controlled 79%.

According to The Center For Public Integrity, during the negotiations on the passage of the "Affordable Care Act" in 2009, 4,525 lobbyists were sent to congress (8 for every member) by various companies to influence the bill, a bill that started off with a universal healthcare program.

In what we eat? Found by ETC group (2008), in the seed industry, just three corporations control 47% of the global market, Monsanto (nearly a quarter alone), DuPont and Syngenta. Mother Jones published in 2010 that;

"Just four companies'Cargill, Archer Daniels Midland, Bunge, and Louis Dreyfus'control up to 90 percent of the global trade in grain. In the United States, three of those firms process 70 percent of the soybeans and 40 percent of the wheat milled into flour. The bulk of corn and soy grown by US farmers ends up feeding animals in vast factories, and here, too, the consolidation is dramatic: Three companies now process more than 70 percent of all beef, and just four firms slaughter and pack upwards of 58 percent of all pork and chicken."

In 2011, Cargill recalled 36 million pounds of turkey for salmonella; Tyson Foods recalled 131 thousand pounds of beef for E. Coli

Senator Bernie Sanders wrote in the Boston Globe (2011):

"Believe it or not, the country's six largest financial institutions (Bank of America, Citigroup, JP Morgan Chase, Wells Fargo, Morgan Stanley and Goldman Sachs) now have amassed assets equal to more than 60 percent of our gross domestic product. The four largest banks issue two-thirds of all credit cards, half of all mortgages, and hold nearly 40 percent of all bank deposits. Incredibly, after we bailed out the behemoth banks that were "too big to fail," three out of the four are now even bigger than before the financial crisis."

During the financial collapse, Goldman Sachs and others were given bail-out loans through the Federal Reserve at rates sometimes as low as 0.01% interest when just before these banks were charging homeowners and students outrages interest rates at 20% and even higher.

Of course I couldn't leave it out, and I'd argue this aspect is not necessarily a direct result of the economic system we practice but linked nonetheless; there are only two, just two, political parties. Are two, limited in scope, political parties supposed to encompass the ideas of the most diverse country on the planet with a population of 300 million people?