Over the course of 2014 the prices the world pays for crude oil have tumbled from over $125 per barrel to around $45 per barrel now, and could easily drop further before heading much higher before collapsing again before spiking again. You get the idea. In the end, the wild whipsawing of the oil market, and the even wilder whipsawing of financial markets, currencies and the rolling bankruptcies of energy companies, then the entities that financed them, then national defaults of the countries that backed these entities, will in due course cause industrial economies to collapse. And without a functioning industrial economy crude oil would be reclassified as toxic waste. But that is still two or three decades off in the future.
In the meantime, the much lower prices of oil have priced most of the producers of unconventional oil out of the market. Recall that conventional oil (the cheap-to-produce kind that comes gushing out of vertical wells drilled not too deep down into dry ground) peaked in 2005 and has been declining ever since. The production of unconventional oil, including offshore drilling, tar sands, hydrofracturing to produce shale oil and other expensive techniques, was lavishly financed in order to make up for the shortfall. But at the moment most unconventional oil costs more to produce than it can be sold for. This means that entire countries, including Venezuela's heavy oil (which requires upgrading before it will flow), offshore production in the Gulf of Mexico (Mexico and US), Norway and Nigeria, Canadian tar sands and, of course, shale oil in the US. All of these producers are now burning money as well as much of the oil they produce, and if the low oil prices persist, will be forced to shut down.
An additional problem is the very high depletion rate of "fracked" shale oil wells in the US. Currently, the shale oil producers are pumping flat out and setting new production records, but the drilling rate is collapsing fast. Shale oil wells deplete very fast: flow rates go down by half in just a few months, and are negligible after a couple of years. Production can only be maintained through relentless drilling, and that relentless drilling has now stopped. Thus, we have just a few months of glut left. After that, the whole shale oil revolution, which some bobbleheads thought would refashion the US into a new Saudi Arabia, will be over. It won't help that most of the shale oil producers, who speculated wildly on drilling leases, will be going bankrupt, along with exploration and production companies and oil field service companies. The entire economy that popped up in recent years around the shale oil patch in the US, which was responsible for most of the growth in high-paying jobs, will collapse, causing the unemployment rate to spike.