Saudi Arabia announced that at least 14 of the 117 Saudis released from Guantanamo Bay, have returned to terrorist activities. At least five percent of those (over 500) released from Guantanamo Bay have returned to terrorist activities. There are still 22 Saudis at Guantanamo Bay, along with about 220 other hard core terrorists. Saudi Arabia said it would either rehabilitate, or keep jailed, those released from Guantanamo Bay. Thus the admission that 14 of these men returned to terrorism (and 11 are still on the loose) is embarrassing. But overall, the rehab program has been a success. Many young men who were leaning towards a life of terrorism, for some good attitude adjustment. But this reminds the Saudis that the hard core will just go through the motions.
The Saudis have arrested several thousand terrorist suspects, and released or rehabilitated most of them, in the last six years. In that time, Saudi Arabia has foiled over a dozen attacks, mainly on oil facilities or foreigners working in the kingdom. While Saudi Arabia is an absolute monarchy, the royal family spreads the wealth around, thus most Saudis are opposed to al Qaeda attempts to damage the oil production and shipment facilities.
Saudi Arabia has formed a special oil and industrial facility protection force of 35,000 security personnel. This is a last ditch defense. It's much better to catch the terrorists while they are still planning their strikes. The Saudis have excelled in maintaining the support of most of the population. This is done largely because the Saud family has always recognized that they rule via the support of a network of tribes and clans. This schmoozing is time consuming, and often aggravating, but it pays off when there is a perceived threat. The al Qaeda bombing campaign in 2003-4 (to "punish" the Saudis for "allowing" the invasion of Iraq) turned most Saudis against Islamic radicals, and the security and intelligence services took advantage of the subsequent flood of tips (there are a lot of al Qaeda fans in the kingdom, but most are talkers, not doers.)
But Saudi counter-terror efforts have to keep in mind that many Saudis support the idea that Islam is under attack (if only culturally) by the West, and that it's generally OK to kill non-Moslems abroad.