When you talk about the risk of software as a service, you can mention that the US gov't is attempting to collect identifying user data from the Wikileaks Twitter account, or the recent domain name seizures of PokerStars and other online gambling websites.
These are practical consequences of a lack of Free Software
Huh Wut!?
How is free or open software going to prevent any company from receiving a court order to disclose data about its users?
This has nothing to do with technical implementation of a service.
Agreed, the point isn't straight-forward. Stallman's argument was against software-as-a-service and in favor of doing computing locally.
If we were using a decentralized twitter alternative like identi.ca or status.net, then all of the IP/log data wouldn't be in Twitter's hands to give in the first place. This is the 'if you let other people do your computing for you, you lose control/freedom over your data' argument.
The same logic (albeit less convincingly) applies to PokerStars - if we were using some sort of Bitcoin-driven, no-single-point-of-failure architecture for online poker, the US government wouldn't have been able to shut down the operation nearly as easily.
These are practical consequences of a lack of Free Software
Huh Wut!?
How is free or open software going to prevent any company from receiving a court order to disclose data about its users?
This has nothing to do with technical implementation of a service.