Totally agree that SLAs are not a guarantee of service - I don't believe I said they were, and I was trying to make the exact same point: too many people treat

Totally agree that SLAs are not a guarantee of service - I don't believe I said they were, and I was trying to make the exact same point: too many people treat them as if they were a guarantee, even when they carry only token penalty clauses. Separately from the SLA, technical promises/guarantees that AWS did make e.g. isolated AZs were broken in the April outage. I think that your proposed model ("machine is online or not") may be sufficiently simple that the AWS cloud can satisfy it; however I think it is very difficult to build anything interesting if that is the only axiom you have. In particular, I would want something related to persistent storage in the model, or else storing state becomes very difficult.