Some of them were actually Bedouin tribespeople who had been convinced to settle down. Where my anecdotal evidence hits a snag is that I actually don't know how far down the totem pole these people actually were, since you had to have some pull somewhere to get the job!
But I can tell you, that the goverment wonks (yeah, they got'em, too) with whom we worked were extremely concerned with the mobs of educated (or semi-educated) kids from the "better" families who were wide open to recruitment by terrorist fundamentalist mullahs. Saudi's, BTW, are just not into the work thing quite yet. Most work in KSA, from the bottom up, is handled by foreigners (including being a government wonk!). Many companies run paralell staffs, with Saudis for show, and foreigners to do the work. This is changing, but very slowly.