The world is using pretty much all the oil that's being produced currently. India and China in particular are using far more than in the past. As the economic cycle cools off, that will drop a bit, and ease the marginal price swings we've been experiencing. But of course, that means less economic activity, i.e., less jobs.
The Saudis can up their output some, but it is going to take a long time. They have to build more infrastructure. I imagine they rather like getting $50 for a barrel, too, which means the incentives are not in our favor.
The refinery shortage in the U.S. has been a problem for a long time. No new refineries have been built for over 30 years, due in part to NIMBY syndrome.
Check out US refinery utilization here:
http://www.eia.doe.gov/oil_gas/petroleum/info_glance/refineryops.htmlUS refineries are running around 92-94% of capacity. That is extremely close to full utilization, leaving almost no margin for problems. Remember also that there are bulges and distortions in the distribution system. Refineries can not ship with equal efficiency to every market.
No supply system (whether it is energy, agriculture, or what have you) can run near its theoretical maximums for long before there is trouble. Unforeseen problems are part of life. Without reserve capacity, we've been begging for trouble. Any disruption spells big price spikes.
Peace.
EDIT: fixed a typo, and rewrote a paragraph to increase clarity.