I like the 3L framework, and would like to extend it to a 4L framework by including Liability.
Software liability is already a difficult topic (see for example Whose fault is it anyway? and Taking on software liability by the BBC technology analyst Bill Thompson). But Software-as-a-Service is more complex, because the liability potentially works both ways. Service providers try to avoid being made responsible for breaches of copyright or data protection, for libel and defamation, or other bad behaviour taking place on its systems.
Fred has mentioned some aspects of liability previously
"hosters ... hosting business need to worry about the risks and liability of hosting third party code" (Enabling the long tail of SaaS providers)but I think it needs a much more systematic treatment. Perhaps some of the leading SaaS bloggers would like to join in?
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