Oil is one the most purchased commodities in the world. With plummeting oil prices many suppliers in places such as Scotland will be driven out of the market. US shale gas is another prime example of a producer that will be driven out of the market. This will, on top of reducing revenues from suppliers and reducing their potential to develop dynamic economies of scale, create mass unemployment leaving may people struggling to provide for their families.
This will have a massive effect on the worldwide economy, but that doesn't mean it is all for the "bad" economy. The price of the barrel below $28 will surely bring gas prices down to below a $1 a gallon, giving everyone the opportunity to travel around more, have more money in their pockets. Once the price of gas goes above $4/gal everyone starts to minimize their outings and spending less money in the economy. When people spend money it effects the economy worldwide.
It is absolutely true that the price of the Oil barrel is influencing all the fields of our economy because we use oil in all activities of our lives. It will fluctuate the prices of all our products, adding as a factor of change to all prices in our everyday life.
We are already seeing the effects of the non stop falling of oil prices. This will have a very big impact on the global economy. It could also force certain countries that rely on oil as their sole source of income to become unstable. Oil prices need to stabilize or things could get very ugly.