There has always been a minority in Saudi Arabia who believed that the goal of Islam was to convert everyone on the planet to Islam. And kill all those who got in the way of this worthy goal. The Saudi zealots were at the same time shamed, and inspired, when the Shia Moslems established an Islamic Republic in Iran back in 1979. Mainstream Islam follows the Sunni practices, and the more conservative Sunni clerics consider the Shia Moslems heretics. This was part of the reason why there was such energetic support for a jihad (religious war) against the Russian occupation of Afghanistan during the 1980s. The Afghans are largely Sunni, the Islamic conservatives from Saudi Arabia went off to help, and perhaps establish Islamic Republics in Afghanistan, Pakistan, and the other "stans" of Central Asia.
Note that this was a very confusing time for Islamic conservatives, for at the same time the jihad was going on against the Russians in Afghanistan, Iraq was fighting the Islamic Republic of Iran. Worse yet, the government of Iraq was run by non-religious Sunni Arabs (the Baath Party, led by Saddam Hussein.) Saudi Arabia supported Iraq because, religious purity aside, the Iranians had, for thousands of years, dominated Arabs, and often treated them harshly. But there was also a religious angle to this support for Iraq, because the newly established Islamic Republic of Iran was preaching world revolution, with Shia Islamic Republics everywhere. Shia and Sunni Islam not only differ in terms of some religious practices, but also in terms of which sect is the "correct" one. Most of the time, Shia and Sunni agree to disagree and let it go at that. But it doesn't take much more than a fiery preacher to get Moslems of one sect moved to violence against members of the other. Usually it is Sunnis beating on Shias, because Sunnis are by far the majority of Moslems. Except in Iran and Iraq, where Shias are the majority.
The economic and political failure of the Iranian Islamic Republic has discouraged many potential Saudi religious zealots. But there are still tens of thousands who are willing to fight. Most never get beyond sitting in a coffee shop boasting about what they are going to do about it some day. The Saudi government made it clear from the beginning that you can talk about jihad all you want, but if you want to do it, go somewhere else. Thus the government helped get young zealots to Afghanistan in the 1980s. And after the young firebrands came home, those that showed rebellious tendencies were stripped of their Saudi citizenship and tossed out of the country. This is what happened to Osama bin Laden. But many zealots kept quiet, and continued to work for organizations like al Qaeda (which was formed during the 1980s as a support organization for the jihad in Afghanistan).
On May 12th of this year, young Saudi zealots brought the jihad home with three attacks on "western" style housing areas where foreigners and "westernized" Saudis lived. The MOI knew something like this was in the works, and had made some arrests. But Saudis now refer to "May 12th" as their "911." Many Saudis had long complained about the growing strength of the Islamic conservatives, and the increasingly radical talk of the wild eyed young men. After May 12th, the government could no longer assure everyone that the radicals understood the rules ("talk and preach, but dont act, at least not in Saudi Arabia.") The Saudi government was quick to react. Thousands of known or suspected Islamic radicals were rounded up. Hundreds of the most radical Islamic clergy, who are all collecting government paychecks, were called in and told to tone it down, or else. When some of these radical clergy kept preaching support for terrorism, members of their congregations turned them in. Pretty soon, you heard less jihad being discussed in coffee houses as well.
The MOI and other police agencies soon discovered that the Islamic radicals were not all talk and bluster. Hundreds of weapons and tons of ammo and explosives were discovered. Interrogation of suspects revealed widespread networks, some of which were rather shadowy and apparently run by people who did not talk freely when interrogated. Moreover, the Saudi population is enraged. Although most Saudis opposed the invasion of Iraq, they are even more opposed to terrorism in their own country. Not only were the Saudi security forces unusually active and efficient after May 12th, but they were more open in cooperating with Western governments (at least on anti-terrorism matters.)
Saudi Arabia's Ministry of Interior (MOI) is waging a far more aggressive campaign against Saudi terrorists than is generally being reported. Partly, this is because the government prefers to operate in without a lot of publicity. Since the country is a monarchy, the Saudis can get away with this. Moreover, the Saudis don't want to admit that the real reason for the secrecy is that the terrorism situation in the kingdom is far worse than they want to admit publicly. For the last two decades, the Saudi government has looked the other way as local Islamic fundamentalists educated a generation of young men to hate non-Moslems, and see holy war (Jihad) against infidels (non-Moslems) as a worthy goal. This generation came of age as the Saudi economy, despite all the oil income, faltered, and the guys who had gone to religious schools were even more likely to be unemployed than those who attended a "western" school and learned engineering or accounting. Too many of these adolescents and young men have nothing better to do than commit themselves to world wide jihad.
After three months, there are results. Not only are the jails full of real, or wannabe, Saudi terrorists, but foreign embassies are allowing diplomat's families to return. The schools for the children of foreigners are opening on schedule this month. The gated communities ("compounds" in local parlance) where most Westerners (and westernized Saudis) live, now look like prison camps. There is more barbed wire, more armed guards, more check points. But at the same time, many more foreigners are being seen outside the compounds, in the malls and in other public places.
Saudis are not any more pro-Western, but they are a lot more anti-terrorist. They look at the terrorism in Iraq and fear that many of the perpetrators may be young Saudis who fled the roundups back home. Because of the government restrictions on news stories, Saudis have developed a highly efficient informal news network (via cell phones and email). And the word is that a lot of radical young men have "gone to jihad in Iraq." Many in the government are content to let these young jihadis get killed by American soldiers, but fear the blowback when a lot of them are captured and revealed to be Saudis on the run. The Saudi government has not been exerting themselves to stop these guys from fleeing north.
Meanwhile, there are raids and gun battles nearly every day in Saudi Arabia. Most of these incidents never make the press. Unless you are plugged into the SINN (Saudi Informal News Network), you'd never know that one of the most active theaters of the War on Terror is Saudi Arabia.