More risks than rewards
To sum up then the arguments against taking the NSA into account in your cloud activities are simple and few.
There's nothing you can do about it anyway so why worry?
The NSA's activities are necessary to protect Americans against terrorism.
The economic advantages of cloud services are too great to ignore despite the security risks.
Against that I argue that the unprecedented surveillance by the NSA is dangerous to the health and security of the Internet; unnecessary to protect Americans against terrorism; and should be addressed by both our elected representatives and major cloud service providers to make the Internet more secure and to increase the transparency of intelligence activities.
The cloud is an important and revolutionary infrastructure. If the United States is to maintain technology leadership we need to be able to assure the entire world that their data and secrets are safe with American technology providers.
Worry about criminals first, NSA after
I have attempted, in this debate, to avoid emotional arguments or assertions of moral authority. If you are making security decisions for a business you really need to do the same or you are not serving your company's interests.
The core of my argument here is that there is nothing about what the NSA has done or is accused of doing which gives reason to take measures that you shouldn't be taking anyway. I'll go a step further here: The NSA is almost certainly uninterested in your cloud data, but there is a large population of criminals who might be. You need to protect your data against them, and that means taking pretty much all the measures you could to impede the NSA. Ergo: Don't worry about the NSA. It accomplishes nothing and confuses the issue. They are just another potential attacker, albeit a highly-sophisticated and heavily-resourced one.