"Cloud computing" is such an ill-defined term. RMS is talking about services like GMail, where users give up privacy and reliability for convenience. Network accessible services that store your personal data have huge ramifications for privacy abuse as well as a very real possibility that they shutdown the service (and if the service doesn't have any data portability, how can you back it up?), or start charging money for the service (maybe a greater amount than you're willing to pay).
This doesn't mean you should give up network services entirely, but you should consider the aspects of the particular service and see whether it's worth it to sacrifice some freedoms for convenience.
The Franklin Street Statement by the FSF represents a good set of guidelines for users and developers of network services.
There's also a developer side to "cloud computing", which are on-demand virtualized web hosting services like Amazon's EC2. I don't think RMS would have a problem with that. As long as the developer retains control over the software and data, there's no difference between that and co-located web-hosting. Except of course if you are using EC2 to build some service like GMail.
As for developers, I've seen many applications that could very well have been desktop software, but the developer decided to make it web-only so they could make it an ad-supported or a subscription service. It's very enticing for developers. They don't have to worry about piracy, their users are locked into the service due to the data being stored there, and you're profiting based on the continued use of the service, rather than a one-time fee. On the other hand, users face substantial risks. As a developers, we have to think twice before we develop such an application that could possibly restrict the freedoms of users.
The number of computer scientists in a room is inversely proportional to the number of bugs in their code.