Gas prices of $15/gallon, over $200/barrel of oil, would be disastrous for this country (US). We already see the middle class disappearing, and this is one more burden that will drive the now middle class into lower class. Everything in our modern society is built upon oil being readily available. Suburbs thrive based upon cheap and readily available oil, but will be obliterated in high oil price economies. People will have to move toward more urban centers, but of course there are occupations where this will not be possible, ranchers, agriculture, etc. Their costs are going to be enormous, which is going to be passed on to consumers of course, and rightly so.
Personally, like another poster said, I too feel we are headed for a cliff at full speed. I think the life we have grown comfortable with and accustomed to is about to take a huge turn. Prices of those magnitudes would spell economic disaster, and descend this country into chaos. Entire industries would collapse, and with millions out of not just jobs but careers, the financial impact will be huge and have far reaching effects. This will knock us back a hundred years, at least. Most people, excluding the very wealthy, will have to cut out entertainment and all non-necessaries from the budget. Just surviving will take up so much money. Food will of course be hugely expensive. People will no longer be able to afford things out of season, as shipping costs will make them to expensive. Most electricity sources will have to jack prices up. Houses will have multiple families in them to pool money, and to reduce the need to travel. Recreational travel will be no more. Goods will no longer be so readily available. It's easy now to order something off the net and have it a few days later, but shipping that stuff by ground, and most especially by air will be exceedingly expensive. Flying will be for the rich only or for very special occasions. Public transit will the modus operandi, and high speed rail lines will need to be built to take the place of many domestic flying routes. Entire cities will have to rethink their infrastructure, transit systems, and zoning rules (cough cough - Houston!!! - get with the times already and have some foresight!!)
I work in the airline industry - and myself and many I know are taking a serious look at the long-term sustainability of our careers given the current energy price trends. My career may not exist in just a couple years at this rate. Thousands have lost their jobs already, mine will most likely be shed by the fall, and thousands more will lose theirs as airlines go under. This ripples out and brings the economy down that much further. This will eventually hit many industries.
As the common folk curb their spending and quit buying anything but necessities, even the rich will feel the pinch as their bottom line takes a nosedive.
Ugly times are ahead - unless something drastic changes. We can drill all we want, and we should, but in the end it only delays the inevitable. We've got to find alternative and sustainable resources asap, we've got to make huge changes most of this nations infrastructure (ie stop urban sprawl) and mass transit (ie - get those high speed rail lines built). I really hope all of the doom and gloom I wrote about doesn't happen, but on our current course it is our future reality. I hope something steers us down a new path as I don't like the on we're on!