Stallman's recent statements regarding his dislike of "cloud computing" didn't surprise me in the least, given what I understand about his software preferences. In fact, I think this is less about Stallman's worry about the security implications of cloud computing, and more about his desire for a software ecosystems that adheres to the principles embodied in the GPL. Stallman simply cannot accept a world where proprietary and open source code live alongside each other in harmony. In that respect, he is a free software purist.
I've known a few "hard core" vegetarians in my life, and one thing I have noticed about them is that they rarely go to restaurants, preferring instead to stay at home and cook their own food under conditions they can control. Cloud computing, by its very nature, assumes that you are passing the handling and processing of your personal information over to a third party. They might be as principled from a software freedom standpoint as Stallman might like, but few - if anyone - can match the bar set by Stallman. Stallman is a man who hates game consoles because they are bastions of the proprietary mindset, and bought an OLPC laptop not because he was interested in its design aspects, but because it was one of the few systems on which he could replace the system BIOS with free GPL-licensed software, thus giving him a 100% "free software" system.
His decision to pick on GMail was telling. Google may be a heavy user of Linux and GPL software in general, but they were strongly against the "Affero" flavor of the GPL license. This clarification, which exists today and is available for software developers to apply to their own code, aimed to close the "web services" loophole. GPL version 2 and 3 both require you to release the source code for any enhancements you make to a GPL-licensed piece of software (a definition which includes code that merely links against binaries, which is why the LGPL exists). That only applies, however, if you release the software as part of a package that third parties can use themselves.
If you don't release the software for third party use, however, the GPL is silent on your obligations. To some, that violates the spirt of the GPL, but "spirit" rarely holds much weight in law courts.
This "loophole" is rather important to Google, because it will be a cold day in hell when they release the enhancements they've made to Linux that support the number one search engine in the world and serves as the foundation of a company worth many billions of dollars. Google has opposed the Affero variation of the GPL since day one for that reason.
In truth, however, Stallman is speaking out about the dangers of ocean surges as the waves come crashing down around his head. I can't see any way to stop the growth of cloud computing, because it offers features that you simply cannot achieve while relying simply on the limited resources most users have available to them on personal computers. In a way, cable television is a cloud service (and becomes more like the modern conception as more networks IP-enable their offerings), and it would be easier to divide the Empire State building in two than it would be to separate the typical American from their modern digital cable television service.
Think about mobile phones for a second. You can only cram so many resources into the small form factor of a typical phone. Cloud computing, however, allows you to have the resource-equivalent of a supercomputer made available to you irrespective of the limitations of that portable communications device.
We are awash in cloud services these days, and pretty much the only way to escape them is to pull back from society and join an Amish commune. That, I think, would be a step too far, even for Stallman. Say what you want about his software philosophies or political predispositions, but he is clearly a man who loves technology.