The overarching driver of American policy in the Middle East has always been oil, with support and sponsorship of Israel a close second. The Cold War certainly complicated the picture as America's pragmatic policy of supporting (often unsavory) regimes to merely counterbalance Soviet satelite states was in full effect. After the fall of communism, however, oil moved front and center. Mind you, it's not so much the oil itself as it is the strategic control of the region. The combined oil reserves of Iran, Iraq, Saudi Arabia and the other smaller Arab nations are tremendous to say the least. The biggest fear from America's point of view is all of that wealth falling under the control of a single Arab super-state: *Islamic or secular*.
And if you think America is concerned about united a Arab nation, Israel is even more so. As George Friedman of Stratfor brilliantly lays out here, Israel's very survival is predicated on keeping the Arab world in warring factions. All the money and technology in the world would not change the fact that Israel is a tiny population compared to rest of the Muslim world, and it would eventually lose a war of attrition against a massive army from Pan-Arab mega state - especially one with nukes.
Historical Case Studies
Nasser was the first leader in the region to try to aggressively unite the Arab World. His regime was predominately secular, and he sought to modernize and industrialize Egypt and ultimately absorb all the other Arab countries from the Sinai Peninsula to the Persian Gulf. He was not a Marxist, but he was a national socialist with a bent towards militarism and industrialism (much like European fascism). Despite a brief merger with Syria forming the short-lived United Arab Republic, Nasser ultimately failed. Sadat eventually took power and was much easier for America to control.
Saddam and the Baathists were inspired by Nasser, and generally shared the same vision. In an effort to stymie Iran's revolutionary momentum in the 1980's, America propped up Saddam to draw Iran into a long and costly war. One of Saddam's stipulations in the agreement was that he could eventually grab Kuwait, and American diplomats basically implied that he could. Saddam eventually decided to take matters into his own hands and invaded Kuwait, and made overtures that there would be a follow on invasion of Saudi Arabia. This upset the balance of power in the region to the level where American intervention was deemed necessary, thus the first Gulf War.
Though many thought that the first Gulf War didn't go far enough, it was still a relatively bold gesture that was noticed throughout the Muslim world, in a highly negative light mostly. Enter Osama bin Laden. Bin Laden felt that the secular approach to uniting the Arab world was a failure. His approach was (and is) to use Islam as the rallying cry for resistance against American influence in the region. Bin Laden too wants to start a domino effect, and his greatest prize would be to topple the House of Saud and replace it something more truthful to Islam (as if it isn't Islamic enough already!). Thus far, bin Laden has been a failure as not one American puppet regime has fallen as a result of his Jihad. However, he is still a lethal threat that we underestimate at our peril. I personally think he is a genius in some respects, albeit an evil one.
But hopefully you can begin to see the general equation, that which has guided American policy in the past and present in the Middle East:
Oil Wealth + United Arab State = possible super power rival and possible destruction of Israel
So while oil isn't the only factor in US policies, it is certainly a major one. And war-for-oil conspiracies are certainly not slowed down by the fact that the oil company once ran by Dick Cheney has made billions and billions of dollars in no bid contracts as a direct result of war prosecuted by himself and his neoconservative cronies.