Very true, but when faced with the possibility they are going to get their equipment from China, N. Korea, Russia, or us, which would we have the best chance of controlling through things like SOSCOE, or as has been mentioned, tracking it through GPS. This also makes the Saudis dependent on us, and thus, our best interest is more vital to their infrastructure. If they acquired this equipment from China, for example, then they would be looking out for China's best interest and we would not have any chance of a SOSCOE type control over the equipment...
There is always more to the story than the first knee jerk reactions a lot of people have.. kind of like Dubai Ports.. we lost an opportunity to have our agents in ports all around the world and all of DPI's ports upgraded with US security measures..
There is also the issue of them reselling, or lending the weapons we sell them to the Chinese, Russians, N. Koreans, etc.
Anything we sell them should not be technology that they couldn't get somewhere else.
At that point, it really becomes a business decision. If they can get the weapons from a number of sources, why not lower the costs of our own weapons by economies of scale by selling them weapons ourselves instead of having them buy them elsewhere.
We just need to make sure our own defense industry doesn't get overzealous and sell such countries weapons with capabilities that they couldn't get elsewhere in an attempt to compete for their business.